Figure 1717

Electron micrographs of gallbladder epithelium, a. The tall columnar cells display features typical of absorptive cells, with microvilli on their apical surface, an apical junctional complex separating the lumen of the gallbladder from the lateral intercellular space, and numerous mitochondria in the apical portion of the cell, x 3,000. b. During active fluid transport, salt is pumped from the cytoplasm into the intercellular space, and water follows the salt. Both salt and water then diffuse...

Morphologic Specializations of the Lateral Cell Surface

Lateral cell surface folds (plicae) create interdigitating cytoplasmic processes of adjoining cells The lateral surfaces of certain epithelial cells show a tortuous boundary due to infoldings or plicae along the border of each cell with its neighbor (Fig. 4.15). These infoldings increase the lateral surface area of the cell and are particularly prominent in epithelia that are engaged in fluid and electrolyte transport, such as the intestinal and gallbladder epithelium. In active fluid...

Figure 1710

Electron micrograph showing the perisinusoidal space (of Disse). The perisinusoidal space (D) is located between the hepatocytes (H) and the sinusoid. A gap (large arrow) separates the endothelial cells (En) that line the sinusoid. Such gaps allow easy passage of small substances between the sinusoid and the perisinusoidal space. Numerous microvilli extend from the hepatocytes into the perisinusoidal space. These processes are long and frequently branch (small arrow). A red blood cell (RBC) is...

Descemetsjmembrane endothelium

Stroma, are low columnar in contrast to the squamous surface cells. Note that one of the surface cells is in the process of desquamation (arrow). X280. c. A higher-magnification photomicrograph of the posterior surface of the cornea covered by a thin layer of simple squamous epithelium (corneal endothelium). These cells are in direct contact with the aqueous humor of the anterior chamber of the eye. Note the very thick Descemet's membrane (basal lamina) of the corneal endothelial cells. x280....

Box

Functional Considerations Hormonal Regulation of Bone Growth Hormones other than PTH and calcitonin have major effects on bone growth. One such hormone is pituitary growth hormone (GH, somatotropin). This hormone stimulates growth in general and, especially, growth of epiphyseal cartilage and bone. Oversecretion in childhood leads to gigantism, an abnormal increase in the length of bones absence or hypose-cretion of somatotropin in childhood leads to failure of growth of the long bones,...

Overview of the esophagus and gastrointestinal tract

The portion of the alimentary canal that extends from the proximal part of the esophagus to the distal part of the anal canal is a hollow tube of varying diameter. This tube has the same basic structural organization throughout its length. Its wall is formed by four distinctive layers. From the lumen outward (Fig. 16.1), they are Mucosa, consisting of a lining epithelium, an underlying connective tissue called the lamina propria, and the muscularis mucosae, composed of smooth muscle Submucosa,...

Plate 46 Tongue Ii

The papillae and their associated taste buds constitute the specialized mucosa of the oral cavity. Although filiform papillae do not have taste buds, the other three types, viz., fungiform, circumvallate, and foliate, contain taste buds in their epithelium. The fungiform (i.e., mushroom-shaped) papillae (see Plate 45) are most numerous near the tip of the tongue. Taste buds are present in the epithelium on their dorsal surface. The taste buds in the epithelium covering the circumvallate and...

Figure 512

Electron micrograph of an elastic fiber. The elastin (E) of the fiber has a relatively amorphous appearance. The fibrillin microfibrils (arrows) are present at the periphery and within the substance of the fiber. A number of collagen fibrils (C) is also present in this electron micrograph. x40,000. Elastic material is a major extracellular substance in vertebral ligaments, larynx, and elastic arteries In elastic ligaments, the elastic material consists of thick fibers interspersed with collagen...

Figure 230

This photomicrograph of a plastic-embedded specimen showing the lamina propria of the small intestine is stained with toluidine blue. The plasma cells, where appropriately oriented, exhibit a clear area in the cytoplasm near the nucleus. These negatively stained regions (arrows) represent extensive accumulation of membranous cisternae that belong to the Golgi apparatus. The surrounding cytoplasm is deeply metachromaticaliy stained because of the presence of...

Vhistophysiology of the kidney

The countercurrent multiplier system creates hyperosmotic urine The term countercurrent indicates a flow of fluid in adjacent structures in opposite directions. The ability to excrete hyperosmotic urine depends on the countercurrent multiplier system that involves three structures Loop of Henle, which acts as a countercurrent multiplier. The ultrafiltrate moves within the descending limb of the thin segment of the loop toward the renal papilla and moves back toward the corticomedullary junction...

Figure 7 lens human HE x360

This micrograph shows a portion of the lens near its equator. The lens consists entirely of epithelial cells surrounded by a homogeneous-appearing lens capsule (LC) to which the zonula fibers attach. The lens capsule is a very thick basal lamina of the epithelial cells. Simple cuboidal lens epithelial cells are present on the anterior surface of the lar connective tissue. Together, this epithelium and underlying connective tissue represents the conjunctiva (Cj). The white opaque appearance of...

Figure 2125

Photomicrograph of human spermatic cord. a. This low-magnification photomicrograph shows a cross section of the spermatic cord containing several structures. These include the ductus deferens, the accompanying testicular artery and vein, and veins of the pampiniform plexus. xl5. Inset. A higher magnification of a pampiniform vein. Note the bundles of longitudinal smooth muscles (cut in cross section) in the tunica adventitia and tunica intima. x55. b. This cross section of the ductus deferens...

Figure 2120

Schematic diagram of development of intratesticular and excurrent duct systems, a. This diagram shows the testis in the seventh week of development before it descends into the scrotal sac. Note that the mesonephric duct and its tubules give rise to the excurrent duct system for the developing testis, b. Sagittal section of a fully developed testis positioned within the scrotum. Note that the seminal vesicles, ejaculatory ducts, ductus deferens, epididymis, and efferent ductules are all...

Parathyroid glands

The parathyroid glands are small endocrine glands closely associated with the thyroid. They are ovoid, a few millimeters in diameter, and arranged in two pairs, constituting the superior and inferior parathyroid glands. They are usually located in the connective tissue on the posterior surface of the lateral lobes of the thyroid gland. However, the number and location may vary. In 2 to 10 of individuals, additional glands are associated with the thymus. Structurally, each parathyroid gland is...

External ear

The auricle is the external component of the ear that collects and amplifies sound The auricle (pinna) is the oval appendage that projects from the lateral surface of the head. The characteristic shape of the auricle is determined by an internal supporting structure of elastic cartilage. Thin skin with hair follicles, sweat glands, and sebaceous glands covers the auricle. The auricle is considered a nearly vestigial structure in humans, compared with its development and role in other animals....

Figure 106

Electron micrograph of skeletal muscle and corresponding molecular structure of a sarcomere, a. This high-magnification electron micrograph shows a longitudinal section of the myofibrils. The I band, which is bisected by the Z line, is composed of barely visible, thin (actin) filaments. They are attached to the Z line and extend across the I band into the A band. The thick filaments, composed of myosin, account for the full width of the A band. Note that in the A band there are additional bands...

Figure 1820

Alveolar Septum

Photomicrographs of emphysema and pneumonia, a. This photomicrograph from the lung of an individual with emphysema shows the partial destruction of interalveolar septa, resulting in permanent enlargement of the air spaces. Note that the changes in the lung parenchyma are accompanied by thickening of the wall of the pulmonary vessels (arrows) and the presence of numerous cells within the air spaces. These cells are the alveolar macrophages and are shown at higher magnification in Figure 18.21....

Plate 40 Eccrine And Apocrine Sweat Glands

Sweat glands are of two types apocrine and eccrine. Apocrine glands have a limited distribution in the human, they are found in the axilla, anogenital region, and mammary areola. Apocrine sweat glands are large tubular structures that are sometimes branched. They empty into the upper portion of the hair follicle and produce a product that becomes odoriferous after being secreted. The product of the apocrine sweat gland is important in other mammals, serving as a sex attractant and a marker of...

Figure 1414

Hair follicle and other skin appendages, a. Diagram showing a hair follicle. Note the cell layers that form the hair shaft and the surrounding external and internal root sheaths. The sebaceous gland consists of the secretory portion and a short duct that empties into the in-fundibulum. The arrector pili muscle accompanies the sebaceous gland its contraction assists in gland secretion and discharge into the infundibulum. The apocrine gland also empties into the infundibulum of the hair follicle....

S mammary glands

Tubuloalveolar Glands

The mammary glands, or breasts, are a distinguishing feature of mammals. During embryologic development, growth and development of breast tissue occur in both sexes. Multiple glands develop along paired epidermal thickenings, called mammary ridges (milk lines), which extend from the developing axilla to the developing inguinal region. In humans, normally only one group of cells develops into a breast on each side. An extra breast (polymastia) or nipple (polythelia) may occur as an inheritable...

Plate 23 Sympathetic And Dorsal Root Ganglia

Ganglia are clusters of neuronal cell bodies located outside the central nervous system (CNS) nerve fibers lead to and from them. Sensory ganglia lie just outside the CNS and contain the cell bodies of sensory nerves that carry impulses into the CNS. Autonomic ganglia are peripheral motor ganglia of the autonomic nervous system (ANS) and contain the cell bodies of postsynaptic neurons that conduct nerve impulses to smooth muscle, cardiac muscle, and glands. Synapses between presynaptic neurons...

Blood Vessels of the Membranous Labyrinth

Arterial blood is supplied to the membranous labyrinth by the labyrinthine artery venous blood drainage is to the venous dural sinuses The blood supply to the external ear, middle ear, and bony labyrinth of the internal ear is derived from vessels associated with the external carotid arteries. The arterial

Figure 1221

Photomicrograph of the ventricular wall containing the conducting system. This photomicrograph shows a Mallory-Azan-stained section of the ventricular wall of a human heart. The upper two thirds of the micrograph is occupied by the endocardium (E) containing a thick layer of Purkinje fibers. The free luminal surface of the ventricle (top) is covered by endothelium and an underlying layer of subendothelial connective tissue (stained blue). The deep layer of endocardium contains the Purkinje...

Plate 24 Peripheral Nerve

Peripheral nerves are composed of bundles of nerve fibers held together by connective tissue and a specialized layer (or layers) of cells, the perineurium. The connective tissue consists of an outer layer, the epineurium, surrounding the whole nerve the perineurium, surrounding bundles of nerve fibers and the endoneurium, associated with individual neurons. Each nerve fiber consists of an axon that is surrounded by a cellular investment called the neurilemma, or the sheath of Schwann. The fiber...

Figure 1219

Photomicrograph of the left atrial and left ventricular wall. a. This photomicrograph shows a sagittal section of the posterior wall of the left atrium and left ventricle. The line of section crosses the coronary (A-V) groove containing the coronary sinus and circumflex branch of the left coronary artery. Note that the section has cut through the fibrous A-V ring of the mitral valve, which provides the attachment site for the muscle of the left atrium and the left ventricle and the cusp of the...

Figure 2018

Diagram illustrating the blood supply to the human adrenal gland. The region of the capsule, the zones within the cortex, and the medulla are indicated. (Modified from Warwick R, Williams PL, eds. Gray's Anatomy. 35th ed. Edinburgh Churchill Livingstone, 1973.) preganglionic sympathetic nerve ending

Structure of Smooth Muscle

Smooth muscle cells possess a contractile apparatus of thin and thick filaments and a cytoskeleton of actin and desmin intermediate filaments The remaining sarcoplasm is filled with thin filaments that form a part of the contractile apparatus. The myosin component of the smooth muscle cell is extremely labile and tends to be lost during tissue preparation. Special techniques can be used, however, to retain the structural integrity of the thick myosin filaments and thus demonstrate them with the...

Figure 1637

Photomicrographs of the anal canal, a. This photomicrograph shows a longitudinal section through the wall of the anal canal. Note the three zones in the anal canal the squamous zone (SQZ) containing stratified squamous epithelium the anal transitional zone (ATI) containing stratified squamous, stratified cuboidal, or columnar epithelium and simple columnar epithelium of the rectal mucosa and the colorectal zone (CRZ) containing only simple columnar epithelium like the rest of the colon. Note...

Figure 171

171 Muscle

This diagram shows the gross view of the diaphragmatic and visceral surface of the liver, with labeled anatomic landmarks found on both surfaces. The enlarged cross-sectional area of the liver (bottom) shows the general microscopic organization of the liver into lobules. Note the presence of hepatic portal triads at the periphery of each lobule, with the terminal hepatic venule (central vein) in the center of the lobule. terminal hepatic venule (central vein)

Ductus Deferens

The ductus deferens is the longest part of the excurrent duct system The ductus deferens (vas deferens) is a direct continuation of the tail of the epididymis (see Fig. 21.1). It ascends along the posterior border of the testis, close to the testicular vessels and nerves. It then enters the abdomen as a component of the spermatic cord, by passing through the inguinal canal. The spermatic cord contains all of the structures that pass to and from the testis. In addition to the ductus deferens,...

Figure 431

Autoradiograph of intestinal gland (crypt). Autoradiograph of crypts in the jejunum of a rabbit that had been injected with tritiated thymidine 8 hours prior to death and fixation. Nearly all of the epithelial cells in this implicative zone of the intestinal mucosa are labeled, indicating that they were synthesizing DNA at the time the animal was injected. X600. (From Parker FG, Barnes EN, Kaye Gl. Gastroenterology 1974 67 607-621.) along the villi to the surface of the intestinal lumen. The...

Corneoscleral Coat

The cornea consists of five layers three cellular layers and two noncellular layers The transparent cornea (see Figs. 23.1 and 23.2) is only 0.5 mm thick at its center and about 1 mm thick peripherally. It consists of three cellular layers that are distinct in both appearance and origin. These layers are separated by two important membranes that appear homogeneous when viewed in the light microscope. Thus, the five layers of the cornea seen in a transverse section are Bowman's membrane...

Figure 153

Unequal Posterior Pharyngeal Muscles

Circumvallate papillae are positioned in a V configuration, separating the anterior two thirds of the tongue from the posterior third. Fungiform and filiform papillae are on the anterior portion of the dorsal tongue surface. The uneven contour of the posterior tongue surface is due to the lingual tonsils. The palatine tonsil is at the junction between the oral cavity and the pharynx. (Specimen Courtesy of Dr. Gunther von Hagen.)

Figure 2230

Photomicrograph of the inner surface of the labia majora. This low-power H& E-stained specimen of the labia majora's inner surface shows its nonkeratinized epithelium (Ep) and abundant sebaceous glands (SG). Two sebaceous ducts (SD) are also evident. Note the continuity of the duct epithelium with the epithelium of the skin and the sebaceous gland epithelium. At this magnification, several smooth muscle bundles can be just barely discerned (arrows). vestibular glands (also called Skene's...

Box 131

Functional Considerations Origin of the Names T Lymphocyte and B Lymphocyte In the early 1960s, investigators using chicken embryos demonstrated that the bursa of Fabricius, a mass of lymphatic tissue associated with the cloaca of birds, was one of the anatomic sites of lymphocyte differentiation. When this tissue was destroyed in the chicken embryos (by either surgical removal or administration of high doses of testosterone), the adult chickens were unable to produce antibodies, leading to...

Plate 54 Gastroduodenal Junction

The gastrocluodenal (pyloric) junction marks the entry into the absoiptive portion of the alimentary canal. Thickening of the circular layer of muscularis externa at this site forms the gastroduodenal (pyloric) sphincter that regulates passage of chyme from stomach to intestine. The mucous secretion of the pyloric glands helps to neutralize the chyme as it enters the intestine. Figure 1, stomach-duodenum, monkey, H& E x40. The junction between the stomach and the duodenum is shown here. Most...

Vtongue

The tongue is a muscular organ projecting into the oral cavity from its inferior surface. Lingual (i.e., pertaining to the tongue) muscles are both extrinsic (having one attachment outside of the tongue) and intrinsic (confined entirely to the tongue, without external attachment). The striated muscle of the tongue is arranged in bundles that generally run in three planes, with each arranged at right angles to the other two. This arrangement of muscle fibers allows enormous flexibility and...

Secondary Follicle

Rounding granulosa cells as the zona pellucida is deposited (see Fig. 22.5). At the same time, slender processes from the granulosa cells develop and project toward the oocyte, intermingling with oocyte microvilli and, occasionally, in-vaginating into the oocyte plasma membrane. The processes may contact the plasma membrane but do not establish cytoplasmic continuity between the cells. The secondary follicle is characterized by a fluid-containing antrum The primary follicle initially moves...

Plate 55 Duodenum

The small intestine is the principal site for the digestion of food and absorption of the products of digestion. It is the longest component of the alimentary canal, measuring over 6 m, and is divided into three segments duodenum (-25 cm) jejunum (-2.5 m) and ileum (-3.5 m). The first portion, the duodenum, receives a partially digested bolus of food (chyme) from the stomach, as well as secretions from the stomach, pancreas, liver, and gallbladder that contain digestive enzymes, enzyme...

Fractures And Bone Repair 201

Clinical Correlations Articular Cartilage and Joint Diseases 183 box 8.2. Clinical Correlations Nutritional Factors in Bone Formation 199 box 8.3. Functional Considerations Hormonal Regulation of Bone Growth 201 Bone is a connective tissue characterized by a mineralized extracellular matrix Bone is a specialized form of connective tissue that, like other connective tissues, consists of cells and extracellular matrix. The feature that distinguishes bone from other connective tissues is...

Figure 1124

Electron micrograph of a peripheral nerve and its surrounding perineurium. a. Electron micrograph of unmyelinated nerve fibers and a single myelinated fiber (MF). The perineurium (P), consisting of several cell layers, is seen at the left of the micrograph. Perineurial cell processes (arrowheads) have also extended into the nerve to surround a group of axons (A) and their Schwann cell as well as a small blood vessel (BV). The enclosure of this group of axons represents the root of a small nerve...

Myofibrils and Myofilaments

The structural and functional subunit of the muscle fiber is the myofibril Skeletal muscles are composed of fascicles, which in turn are composed of individual muscle fibers. The muscle fiber is filled with longitudinally arrayed subunits called myofibrils (Fig. 10.3). Myofibrils are visible in favorable histologic preparations and are best seen in cross sections of muscle fibers. In these sections they give the fiber a stippled appearance. Myofibrils extend the entire length of the muscle...

Supporting Tissues of the Teeth

Tissues Teeth

Supporting tissues of the teeth include the alveolar bone of the alveolar processes of the maxilla and mandible, periodontal ligaments, and gingiva. The alveolar processes of the maxilla and mandible contain the sockets or alveoli for the roots of the teeth The alveolar bone proper, a thin layer of compact bone, forms the wall of the alveolus (see Fig. 15.7) and is the bone to which the periodontal ligament is attached. The rest of the alveolar process consists of supporting bone. The surface...

Connective Tissue Components of a Peripheral Nerve

The bulk of a peripheral nerve consists of nerve fibers and their supporting Schwann cells. The individual nerve fibers and their associated Schwann cells are held together by connective tissue organized into three distinctive components, each with specific morphologic and functional characteristics (Fig. 11.24 also, see Fig. 11.3). These components are Endoneurium, which includes loose connective tissue surrounding each individual nerve fiber Perineurium, which includes specialized connective...

Anchoring Junctions

Anchoring junctions provide lateral adhesions between epithelial cells, using proteins that link into the cytoskeleton of the adjacent cells. Two types of anchoring cell-to-cell junctions can be identified on the lateral cell surface Zonula adherens (pi., zonulae adherentes), which interacts with the network of actin filaments inside the cell Macula adherens (pi., maculae adherentes) or desmo-some, which interacts with intermediate filaments In addition, two other types of anchoring junctions...

Plate 99 Mammary Gland Late Proliferative And Lactating

Mammary glands exhibit a number of changes during pregnancy in preparation for lactation. Lymphocytes and plasma cells infiltrate the loose connective tissue as the glandular tissue develops. As the cells of the glandular portion proliferate by mitotic division, the ducts branch and alveoli begin to develop at their growing ends. Alveolar development becomes most prominent in the later stages of pregnancy, and accumulation of secretory product takes place in the alveoli. At the same time,...

Plate 11 Bone Ground Section

Bone is a specialized connective tissue characterized by a mineralized extracellular matrix. Calcium phosphate, in the form of hydroxyapatite crystals (CaU)(P04)ft0H2), is deposited along the collagen fibrils and in the proteoglycan ground substance. Bone serves as a storage site for calcium and phosphate, which can be released to the blood to maintain homeostatic levels. Osteocytes reside in lacunae in the bone matrix and extend fine cellular processes into canaliculi that connect the lacunae,...

Info

Largest organelle within the cell with distinct boundary often visible nucleoli and chromatin pattern regions Roughly circular, basophilic region within the nucleus visible in living cells throughout interphase with Interference microscopy Often observed as a basophilic region of cytoplasm referred as ergastoplasm Not visible cytoplasm in region of sER may exhibit distinct eosinophilia Sometimes observed as negative-staining region appears as network in heavy-metal-stained preparations visible...

Figure 2131

Photomicrograph of corpus spongiosum, a. This photomicrograph of a H& E-stained section shows the corpus spongiosum and urethra. x20. b. This higher magnification of the corpus spongiosum shows the numerous irregularly shaped vascular spaces. Note the surrounding layer of smooth muscle (SM) forming the subendothelial cushions. X135. Erection of the penis is a vascular event initiated by the CNS and maintained by complex interactions between vascular and neurologic events. The CNS responds to...

Figure 131

Overview of the structures constituting the lymphatic system. Because lymphatic tissue is the main component of some organs, they are regarded as organs of the lymphatic system (spleen, thymus, lymph nodes). Lymphatic tissue is present as part of other organs, such as red bone marrow, lymphatic nodules of the alimentary canal (tonsils, vermiform appendix, gut-associated lymphatic tissue GALT ) and of the respiratory system (bronchus-associated lymphatic tissue IBALT ), and, not shown in the...

Plate 34 Lymph Node Ii

Immunocompetent B cells that have been exposed to an antigen that they can recognize and bind migrate to a lymph node, where they undergo blastic transformation and begin a series of mitotic divisions that produce large numbers of immature im-munoblasts. The immunoblasts proliferate further and then differentiate into a clone of lymphocytes that differentiate into an-tibody-secreting plasma cells and memory cells. Immunocompetent T lymphocytes behave in a similar manner but differentiate into...

Schwann Cells and the Myelin Sheath

Axons in the peripheral nervous system are described as myelinated or unmyelinated Myelinated axons are surrounded by a lipid-rich layer called the myelin sheath. External to, and contiguous with, the myelin sheath is a thin layer of Schwann cell cytoplasm called the sheath of Schwann, or the neurilemma (Fig. 11.10). This layer contains the nucleus and most of the organelles of the Schwann cell. Surrounding the Schwann cell is a basal or external lamina. Functionally, the myelin sheath with its...

Plate 69 Wall Of Terminal Bronchiole Respiratory Bronchiole And Alveolus

Respiratory bronchioles continue to divide to form alveolar ducts, passages lined solely with rows of alveoli that have rings of smooth muscle in knob-like interalveolar septa. The alveolar ducts terminate in alveolar sacs, enlarged spaces surrounded by clusters of alveoli that open into the spaces. The alveoli are lined with type I alveolar cells, extremely thin squamous cells that cover about 95 of the alveolar surface, and with type II alveolar cells, cuboidal cells that secrete surfactant,...

Structure of the Testis

The testes have an unusually thick connective tissue capsule, the tunica albug nea An unusually thick, dense connective tissue capsule, the tunica albug nea, covers each testis (Fig. 21.4). The inner part of this capsule, the tunica vasculosa, is a loose connective tissue layer that contains blood vessels. Each testis is divided into approximately 250 lobules by incomplete connective tissue septa that project from the capsule. Along the posterior surface of the testis, the tunica albug nea...

Plate 44 Lip A Mucocutaneous Junction

The lips are the entry point of the alimentary canal. Here, the thin keratinized epidermis of face skin changes to the thick parakeratinized epithelium of the oral mucosa. The transition zone, the red portion of the lips, is characterized by deep penetration of connective tissue papillae into the base of the stratified squamous keratinized epithelium. The blood vessels and nerve endings in these papillae are responsible for both the color and the exquisite touch sensitivity of the lips. A H&...

Figure 2216

Histology Contain Myometrium

Photomicrograph of a sagittal section of a human uterus. This section shows the three layers of the uterine wall the endometrium, the innermost layer that lines the uterine cavity the myometrium, the middle layer of smooth muscle and the perimetrium, the very thin layer of peritoneum that covers the exterior surface of the uterus. The deep portion of the myometrium contains the larger blood vessels (BV) that supply the uterus. x8. the development of new fibers through the division of existing...

Thyroid gland

The thyroid gland is located in the anterior neck region adjacent to the larynx and trachea The thyroid gland is a bilobate endocrine gland located in the anterior neck region and consists of two large lateral lobes connected by an isthmus, a thin band of thyroid tissue. The two lobes, each 5 cm in length, 2.5 cm in width, and 20 to 30 g in weight, lie on either side of the larynx and upper trachea. The isthmus crosses anterior to the upper part of the trachea. A pyramidal lobe often extends...

O Histochemistry And Cytochemistry

Specific chemical procedures can provide detailed information about the function of the cells and extracellular components of the tissues Histochemical and cytochemical procedures may be based on specific binding of a dye, use of a fluorescent dye-labeled antibody to a particular cell component, or the inherent enzymatic activity of a cell component. In addition, many large molecules found in cells can be localized by autoradiography, in which radioactively tagged precursors of the molecule are...

Serosa and Adventitia

Meissner And Auerbach Plexus

Serosa or adventitia constitutes the outermost layer of the alimentary canal The serosa is a serous membrane consisting of a layer of simple squamous epithelium, called the mesothelium, and a small amount of underlying connective tissue. It is equivalent to the visceral peritoneum described in gross anatomy. The serosa is the most superficial layer of those parts of the digestive tract that are suspended in the peritoneal cavity. As such, the serosa is continuous with both the mesentery and the...

Plate 22 Smooth Muscle

Smooth muscle is the simplest appearing muscle tissue and is the intrinsic muscle of the alimentary canal, blood vessels, genitourinary tract, respiratory tract, and other hollow and tubular organs. Smooth muscle generally occurs as bundles or sheets of elongated fusiform cells, also called fibers. Smooth muscle is specialized for slow, prolonged contraction. There are no direct neural endings on smooth muscle cells nerve terminals in smooth muscle are in the immediately adjacent connective...

Muscularis Externa

In most parts of the digestive tract, the muscularis externa consists of two concentric and relatively thick layers of smooth muscle. The cells in the inner layer form a tight spiral, described as a circularly oriented layer those in the outer layer form a loose spiral, described as a longitudinally oriented layer. Located between the two muscle layers is a thin connective tissue layer. Within this connective tissue lies the myenteric plexus (Auerbach's plexus) containing nerve cell bodies...

Diffuse Lymphatic Tissue and Lymphatic Nodules

Diffuse lymphatic tissue and lymphatic nodules guard the body against pathogenic substances and are the site of the initial immune response The alimentary canal, respiratory passages, and genitourinary tract are guarded by accumulations of lymphatic tissue that are not enclosed by a capsule. Lymphocytes and other free cells of this tissue are found in the lamina propria (subepithelial tissue) of these tracts. This form of lymphatic tissue is called diffuse lymphatic tissue or mucus-associated...

Figure 1119

Protoplasmic astrocyte in the gray matter of the brain. This schematic drawing shows the foot processes of the protoplasmic astrocyte terminating on a blood vessel and the axonal process of a nerve cell. The foot processes terminating on the blood vessel contribute to the blood-brain barrier. The bare regions of the vessel as shown in the drawing would be covered by processes of neighboring astrocytes, thus forming the overall barrier. limitans, a relatively impermeable barrier surrounding the...

Plate 17 Granulocytes

Granulocytes are characterized by a lobed nucleus and by the specific staining characteristics of granules in the cytoplasm. Three kinds of granulocytes are present in a peripheral blood smear neutrophils (polymorphonuclear leukocytes), 55 to 60 eosinophils, 2 to 5 and basophils, 1 or less. All of the granulocytes leave the bloodstream and enter the connective tissue to perform their specific functions. Neutrophils are actively phagocytic cells that have both specific granules and azurophilic...

Kidney Lobes and Lobules

Lobe The Kidney

The number of lobes in a kidney equals the number of medullary pyramids Each medullary pyramid and the associated cortical tissue at its base and sides (one half of each adjacent renal column) constitutes a lobe of the kidney. The lobar organ ization of the kidney is conspicuous in the developing fetal kidney (Fig. 19.5). Each lobe is reflected as a convexity on the outer surface of the organ, but they usually disappear after birth. The surface convexities typical of the fetal kidney may...

Figure 105

Sarcomeres in different functional stages. In the resting state (middle), interdigitation of thin (actin) and thick (myosin) filaments is not complete the H and I bands are relatively wide. In the contracted state (bottom), the interdigitation of the thin and thick filaments is increased according to the degree of contraction. In the stretched state (top), the thin and thick filaments do not interact the H and I bands are very wide. The length of the A band always remains the same and...

Absorptive Cells

That drives Na+ and water across the basal lamina into the connective tissue. , In epithelia with more permeable tight junctions, such as those in the duodenum and jejunum, a sodium pump also creates low intracellular Na+ concentration. When the contents that pass into the duodenum and jejunum are hypotonic, however, considerable absorption of water, along with additional Na+ and other small solutes, takes place directly across the tight junctions of the enterocytes into the intercellular...

Acidic And Basic Dyes

Hematoxylin and eosin are the most commonly used dyes in histology An acidic dye, such as eosin, carries a net negative charge on its colored portion and is described by the general formula Na+dye . A basic dye carries a net positive charge on its colored portion and is described by the general formula dye+CI J. Hematoxylin does not meet the definition of a strict basic dye but has properties that closely resemble those of a basic dye. The color of a dye is not related to whether it is basic or...

Plate 75 Urinary Bladder

The urinary bladder receives the urine from the two ureters and stores it until neural stimulation causes it to contract and expel the urine via the urethra. It, too, is lined with transitional epithelium. Beneath the epithelium and its underlying connective tissue, the wall of the urinary bladder contains smooth muscle that is usually described as being arranged as an inner longitudinal layer, a middle circular layer, and an outer longitudinal layer. As in most distensible hollow viscera that...

The Contraction Cycle

Shortening of a muscle involves rapid contraction cycles that move the thin filaments along the thick filament. Each contraction cycle consists of five stages attachment, release, bending, force generation, and reattachment. Attachment is the initial stage of the contraction cycle, in which the myosin head is tightly bound to the actin molecule of the thin filament At the beginning of the contraction cycle, the myosin head is tightly bound to the actin molecule of the thin filament, and ATP is...

Figure

Treating Lipomas Naturally

Photomicrograph of brown adipose tissue from a newborn in a H& E-stained paraffin preparation. The ceils contain fat droplets of varying size. Note the large blood vessels within the tissue. xl50. b. This photomicrograph obtained at a higher magnification shows the brown adipose cells with round and often cen trally located nuclei. Most of the cells are polygonal and are closely packed, with numerous lipid droplets. In some cells, large lipid droplets displace nuclei...

Plate 65 Olfactory Mucosa

Olfactory mucosa is located in the roof and part of the walls of the nasal cavity. Its pseudostratified epithelium is thicker than that of nonsensory epithelium, and it serves as the receptor for smell. Olfactory epithelium consists of olfactory cells, supporting (sustentacular) cells, basal cells, and brush cells (see Fig. 18.3, page 582). Olfactory cells are bipolar neurons. The apex of the cell is expanded into the olfactory vesicle from which nonmotile cilia, the actual receptors, extend...

Plate 35 Spleen I

The spleen is the largest lymphatic organ it is surrounded by a capsule and located in the path of the bloodstream (splenic artery and vein). The spleen filters the blood and reacts immunologically to blood-borne antigens. It has both morphologic and immunologic filtering functions. The substance of the spleen, the splenic pulp, consists of red pulp and white pulp, so named because of their appearance in fresh tissue. The white pulp is rich in lymphocytes that form a periarterial lymphatic...

Maternal Circulation

Exchange of gases and metabolic products occurs. The maternal blood finally leaves the intervillous space (black arrows) through endometrial veins. The fetal blood enters the placenta through the umbilical arteries that divide into a series of radially disposed arteries within the chorionic plate. Branches from the vessels pass into the main stem villi and there form extensive capillary networks. The veins within the villi then cany the blood back through a system of veins that parallels the...

Seminiferous tubules Cycle of the Seminiferous Epithelium

Differentiating spermatogenic cells are not arranged at random in the seminiferous epithelium specific cell types are grouped together. These groupings or associations occur because intercellular bridges are present between the progeny of each pair of type Ap spermatogonia and because the synchronized cells spend specific times in each stage of maturation. All phases of differentiation occur sequentially at any given site in a seminiferous tubule as the progeny of stem cells remain connected by...

Plate 80 Adrenal Gland I

There are two adrenal glands, one at the upper pole of each kidney. The gland is a composite of two distinct structural and functional components a cortex and a medulla. The cortex develops from mesoderm and secretes steroid hormones the medulla develops from neuroectoderm of the neural crest and secretes catecholamines. The cortex is divided into three zones according to the type and arrangement of its parenchymal cells. These are designated zona glomerulosa, zona fasciculata, and zona...

Accessory Structures of the

Lacrimal And Tarsal Glands

The conjunctiva lines the space between the inner surface of the eyelids and the anterior surface of the eye lateral to the cornea The conjunctiva is a thin, transparent mucous membrane that extends from the corneoscleral limbus located on the lateral margin of the cornea across the sclera (bulbar conjunctiva) and covers the internal surface of the eyelids (palpebral conjunctiva). It consists of a stratified columnar epithelium containing numerous goblet cells and rests on a lamina propria...

Structure of Cardiac Muscle

The cardiac muscle nucleus lies in the center of the cell The central location of the nucleus in cardiac muscle cells is one feature that helps distinguish them from multinucleated skeletal muscle fibers, whose nuclei lie immediately under the plasma membrane. The transmission electron microscope (TEM) reveals that the myofibrils of cardiac muscle separate to pass around the nucleus, thus outlining a biconical juxtanuclear region in which the cell organelles are concentrated. This region is...

Visceral Surface

Central And Hepatic Vein

Prothrombin and fibrinogen, important components of the blood-clotting cascade. Nonimmune a- and -globulins, which also help maintain plasma colloid osmotic pressure and serve as carrier proteins for various substances (see Chapter 9, page 216). The liver stores and converts several vitamins and iron Several vitamins are taken up from the bloodstream and are then stored and or biochemically modified by the liver. They include Vitamin A (retinol), an important vitamin in vision. Vitamin A is...

Plate 81 Adrenal Gland Ii

The cells of the adrenal medulla develop from the same source as the postganglionic cells of the sympathetic nervous system. They are directly innervated by preganglionic cells of the sympathetic system and may be regarded as modified postganglionic cells that are specialized to secrete. These cells produce the catecholamines epinephrine and norepinephrine. The adrenal medulla receives its blood supply via two routes by arterioles that pass through the cortex and by capillaries that continue...

The Lateral Domain And Its Specializations In Celltocell Adhesion

The lateral domain of epithelial cells is in close contact with the opposed lateral domains of neighboring cells. Like the other domains, the lateral domain is characterized by the presence of unique proteins, in this case the adhesion molecules that are part of junctional specializations. The molecular composition of the lipids and proteins that form the lateral cell membrane differ significantly from the composition of those that form the apical cell membrane. In addition, the lateral cell...

Testis

The adult testes are paired ovoid organs that lie within the scrotum, located outside the body cavity. Testes are sus Intermediate mesoderm that forms the urogenital ridges on the posterior abdominal wall Mesodermal epithelium (coelomic mesothelium) that lines the urogenital ridges

Bulbourethral Glands

Muscle Cells

The bulbourethral glands secrete preseminal fluid The paired bulbourethral glands Cowper's glands are pea-sized structures located in the urogenital diaphragm see Fig. 21.1 . The duct of each gland passes through the inferior fascia of the urogenital diaphragm and joins the initial portion of the penile urethra. The glands are compound tubuloalveolar glands that structurally resemble mucus secretory glands Fig. 21.29 . The simple columnar epithelium, which varies considerably in height...

Plate 61 Liver I

The liver is the largest mass of glandular tissue in the body and the largest internal organ. It is unique because it receives its major blood supply from the hepatic portal vein, which carries venous blood from the small intestine, pancreas, and spleen. Thus the liver is directly in the pathway that conveys materials absorbed in the intestine. This gives the liver the first exposure to metabolic substrates and nutrients it also makes the liver the first organ exposed to noxious and toxic...

Plate 60 Anorectal Junction

At the anorectal junction, there is a transition from the simple columnar epithelium of the intestinal mucosa to the keratinized stratified squamous epithelium of the skin. Between these two distinctly different epithelia there is a narrow region where the epithelium is first stratified columnar or stratified cuboidal and then nonkeratinized stratified squamous. At the level of the anorectal junction, the muscularis mucosae disappears. At the same level, the circular layer of the mus-cularis...

Dendrites and Axons

Axon Hillock

Dendrites are receptor processes that receive stimuli from other neurons or from the external environment The main function of dendrites is to receive information from other neurons or from the external environment and carry that information to the cell body. Generally, dendrites are located in the vicinity of the cell body. They have a greater diameter than axons, are unmyelinated, are usually tapered, and form extensive arborizations called den-dritic trees. Dendritic trees significantly...

Plate 15 Intramembranous Bone Formation

Figure 1, fetal head, human, Mallory trichrome x45. A cross section of the developing lower jaw bone, as seen at this relatively early stage of development, consists of bone spicules BS of various sizes and shapes. The bone spicules interconnect and, in three dimensions, have the general shape of the mandible. Other structures present that will assist in orientation include developing teeth DT , the tip of Meckel's cartilage MC , also referred to as the mandibular process, seen on the left...

Plate 3 Stratified Epithelia And Epithelioid Tissues

Figure 1, esophagus, monkey, H amp E x250 This part of the wall of the esophagus reveals two different epithelia. On the left is the lining epithelium of the esophagus. It is multilayered with squamous surface cells therefore, it is a stratified squamous epithelium SS . On the right is the duct of an esophageal gland cut in several planes. By examining a region where the plane of section is at a right angle to the surface, the true character of the epithelium becomes apparent. In this case, the...

Plate 4 Loose And Dense Connective Tissue

Connective Tissue Mammary Gland

Figure 1, mammary gland, human, H amp E x160 This micrograph shows, at low magnification, loose connective tissue LCT immediately surrounding the gland epithelium Ep . It is relatively less strained with eosin, compared with the dense connective tissue DCT that occupies much of the field. The dense connective tissue, with its numerous thick fibers, is in contrast to the loose connective tissue that has a relative paucity of fibers. The typical wispy nature of the collagen fibers found in loose...

Epithelial Cell Renewal

Most epithelial cells have a finite life span less than that of the whole organism Surface epithelia and epithelia of many simple glands belong to the category of continuously renewing cell populations. The rate of cell turnover, i.e., the replacement rate, is characteristic of a specific epithelium. For example, the cells lining the small intestine are renewed every 4 to 6 days in humans. The replacement cells are produced by mitotic activity in the lower portion of the intestinal glands...

Cyclic Changes During the Menstrual Cycle

Cyclic changes of the endometrium during the menstrual cycle are represented by the proliferative, secretory, and menstrual phases The menstrual cycle is a continuum of developmental stages in the functional layer of the endometrium. It is ultimately controlled by gonadotropins secreted by the pars dis-talis of the pituitary gland that regulate the steroid secretions of the ovary. The cycle normally repeats every 28 days, during which the endometrium passes through a sequence of morphologic and...

Plate 5 Dense Regular Connective Tissue Tendons And Ligaments

Figure 1, tendon, longitudinal section, human, H amp E x100. This specimen includes the surrounding dense irregular connective tissue of the tendon, the epitendineum Ept . The tendon fascicles TF that make up the tendon are surrounded by a less dense connective tissue than that associated with the epitendineum. In longitudinal sections such as this, the connective tissue that surrounds the individual fascicles, the endotendineum Ent , seems to disappear at certain points, with the result that...

Vascular Coat Uvea

Anterior Pigment Myoepithelium

The iris, the most anterior part of the vascular coat, forms a contractile diaphragm in front of the lens The iris arises from the anterior border of the ciliary body Fig. 23.7 and is attached to the sclera about 2 mm posterior to the corneoscleral junction. The pupil is the central aperture of this thin disc. The iris is pushed slightly forward as it changes in size in response to light intensity. It consists of highly vascularized connective tissue stroma that is covered on its posterior...

Olfactory Segment of the Nasal Cavity

Bowman Glands Olfactory Epithelium

The olfactoiy segment is located on part of the dome of each nasal cavity and, to a variable extent, the contiguous lateral and medial nasal walls. It is lined with a specialized olfactoiy mucosa. In living tissue, this mucosa is distinguished by its slight yellowish brown color caused by pigment in the olfactoiy epithelium and the associated olfactory glands. In humans, the total surface area of the olfactory mucosa is only a few square centimeters in animals with an acute sense of smell, the...

Plate 27 Spinal Cord

The spinal cord is organized into two discrete parts. The outer part, called the white matter of the cord because of its appearance in unfixed specimens, contains ascending and descending nerve fibers. Some of the fibers go to and from the brain, whereas others connect different levels of the spinal cord. The inner part of the spinal cord, called the gray matter because of its appearance in unfixed specimens, contains the cell bodies of neurons as well as nerve fibers. The gray matter forms an...

Figure 1420

Photomicrograph showing a late stage in the epidermal repair of a skin wound. The initial injury was caused by an incision through the full thickness of the skin and partially into the hypodermis, which contains adipose ceils A . The epidermis has re-formed beneath the scab. The asterisk marks an artifact where epithelium separated during specimen preparation. The scab, which contains numerous dead neutrophils in its inferior aspect, is close to the point of release. The dermis at this stage...

Figure 514

Photomicrograph of a connective tissue specimen fixed with glutaraldehyde, embedded in plastic, and stained with H amp E. Thin strands of fibroblast cytoplasm arrow 5 belonging to a few preferentially oriented cells can just barely be recognized between collagen fibers. In routine H amp E-stained, paraffin-embedded preparations, it is usually impossible to distinguish the attenuated and poorly preserved fibroblast cytoplasm from the collagen fibers. Typically,...

Plate 20 Cardiac Muscle

Cardiac muscle consists of fibers that possess the same arrangement of contractile filaments and thus the same cross-banding patterns that are present in striated skeletal and visceral muscle. Although cardiac muscle is, therefore, also striated, it differs in many significant respects from skeletal and striated visceral muscle. Cardiac muscle consists of individual cells that are joined by complex junctions to form a functional unit fiber . The histologically obvious differences between...

Dermis

Attachment of epidermis to dermis is enhanced by an increased interface between the two tissues The junction between the dermis and epidermis is seen in the light microscope as an uneven boundary except in the thinnest skin. Sections of skin cut perpendicular to the surface reveal numerous finger-like connective tissue protrusions, dermal papillae, that project into the undersurface of the epidermis see Figs. 14.1 and 14.2 . The papillae are complemented by what appear to be similar epidermal...

Functional Aspects of Smooth Muscle

Smooth muscle is specialized for slow, prolonged contraction As noted above, smooth muscle cells may remain contracted for long periods of time without fatiguing. They may contract in a wave-like manner, producing peristaltic movements such as those in the gastrointestinal tract and the male genital tract, or contraction may occur along the entire muscle, producing extrusive movements, e.g., those in the urinary bladder, gallbladder, and uterus. Smooth muscle exhibits a spontaneous contractile...