1. Body cavities a. The axial portion of the body contains the dorsal and ventral cavities.
(1) The dorsal cavity includes the cranial cavity and vertebral canal.
(2) The ventral cavity includes the thoracic and abdominopelvic cavities, which are separated by the diaphragm.
b. The organs within a body cavity are called viscera.
c. Other body cavities include the oral, nasal, orbital, and middle ear cavities.
2. Thoracic and abdominopelvic membranes
Parietal serous membranes line the walls of these cavities;
visceral serous membranes cover organs within them.
They secrete serous fluid.
a. Thoracic membranes
(1) Pleural membranes line the thoracic cavity and cover the lungs.
(2) Pericardial membranes surround the heart and cover its surface.
(3) The pleural and pericardial cavities are potential spaces between these membranes.
b. Abdominopelvic membranes
(1) Peritoneal membranes line the abdominopelvic cavity and cover the organs inside.
(2) The peritoneal cavity is a potential space between these membranes.
3. Organ systems
The human organism consists of several organ systems.
Each system includes interrelated organs.
(1) The integumentary system covers the body.
(2) It includes the skin, hair, nails, sweat glands, and sebaceous glands.
(3) It protects underlying tissues, regulates body temperature, houses sensory receptors, and synthesizes substances.
b. Skeletal system
(1) The skeletal system is composed of bones and the ligaments and cartilages that bind bones together.
(2) It provides framework, protective shields, and attachments for muscles; it also produces blood cells and stores inorganic salts.
c. Muscular system
(1) The muscular system includes the muscles of the body.
(2) It moves body parts, maintains posture, and produces body heat.
d. Nervous system
(1) The nervous system consists of the brain, spinal cord, nerves, and sense organs.
(2) It receives impulses from sensory parts, interprets these impulses, and acts on them, stimulating muscles or glands to respond.
e. Endocrine system
(1) The endocrine system consists of glands that secrete hormones.
(2) Hormones help regulate metabolism by stimulating target tissues.
f. Digestive system
(1) The digestive system receives foods, breaks down nutrients into forms that can pass through cell membranes, and eliminates materials that are not absorbed.
(2) Some digestive organs produce hormones.
(3) The digestive system includes the mouth, tongue, teeth, salivary glands, pharynx, esophagus, stomach, liver, gallbladder, pancreas, small intestine, and large intestine.
g. Respiratory system
(1) The respiratory system provides for intake and output of air and for exchange of gases between the blood and the air.
(2) It includes the nasal cavity, pharynx, larynx, trachea, bronchi, and lungs.
h. Cardiovascular system
(1) The cardiovascular system includes the heart, which pumps blood, and the blood vessels, which carry blood to and from body parts.
(2) Blood transports oxygen, nutrients, hormones, and wastes. i. Lymphatic system
(1) The lymphatic system is composed of lymphatic vessels, lymph nodes, thymus, and spleen.
(2) It transports lymph from tissue spaces to the bloodstream and carries certain fatty substances away from the digestive organs. Lymphocytes defend the body against disease-causing agents.
j. Urinary system
(1) The urinary system includes the kidneys, ureters, urinary bladder, and urethra.
(2) It filters wastes from the blood and helps maintain fluid and electrolyte balance.
(1) The reproductive system enables an organism to produce progeny.
(2) The male reproductive system includes the scrotum, testes, epididymides, vasa deferentia, seminal vesicles, prostate gland, bulbourethral glands, urethra, and penis, which produce, maintain, and transport male sex cells.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.