B

í

Condensation of' mesenchyme

Condensation of' mesenchyme

Solid cylindrical downgrowth

14 weeks of gestation

Solid cylindrical downgrowth

Primordium of sebaceous

Hair shaft Hair papilla

Hair shaft Hair papilla

Development of lumen

16 weeks of gestation

Vernix caseosa

Sebaceous gland

Vernix caseosa

Sebaceous gland

Hair

Blood vessels in papilla

Blood vessels in papilla

Hair

Erector pili muscle

Bulb

Erector pili muscle

Bulb

Sebaceous gland and hair follicle

18 weeks of gestation

Sweat gland

Glands of the Skin into the secondary connective tissue and forms alveoli. The central cells of the branched alveoli break down to form an oily secretion, the sebum. It is extruded into the hair follicle and then to the surface of the skin. In the fetus, sebum mixes with desquamated peridermal cells and forms the vernix caseosa. In the child and adult, it produces oil for the skin.

Two kinds of sweat glands occur: eccrine and apocrine sweat glands. The eccrine sweat glands develop first as solid epidermal downgrowths into the underlying dermis. The lower ends coil up and form the secretory portion of the gland. The central cells then degenerate, forming a lumen. The peripheral cells of the gland differentiate into secretory and myoep-ithelial cells. The myoepithelial cells are thought to form smooth muscles which help to expel the secreted sweat. The apocrine sweat glands are situated primarily in the axillary area, the pubic area, and around the nipple, but they also occur around the nose, in the outer ear canal, and on the eyelids. These glands form from the epidermis that gives rise to hair follicles. The ducts open, in contrast to the eccrine glands, not onto the skin surface but into the hair follicles just above the opening of the sebaceous glands. Developmental abnormalities in all three kinds of glands can occur.

Quantitation of the Number of Sweat Glands

There are normally about 2 million sweat glands on the surface of the skin. To assess the number of sweat glands on the skin surface, several different techniques exist. Most ignore the apocrine sweat glands.

Chemical Method A solution of o-phthaldialdehyde in xylene can be put on the skin. The chemical produces a black color if sweat is excreted, designating the sweat pores.

Stereomicroscopy Using a 7 objective of a stereomicroscope, the sweat pores on the epidermal ridges of the fingertips can be quantitated by recording the number of pores along 0.5 cm of a dermal ridge. A transparent plastic template with an open square of 0.5 cm per side is used. The count should be performed on 10 ridges from 10 different fingers (Fig. 11.4).

Electron Microscopy A more accurate way to quantitate sweat glands is to determine the number of glands seen on electron microscopic examination of a skin biopsy.

Alternative A further method is to use a dermatoglyphic fingerprint and count the sweat pores on the fingerprint using a microscope or other high magnification device (Fig. 11.4).

Skin area

No.

Forehead

113 (>60 years, 83)

Dorsum of hand

130 (>60 years, 89)

Shoulder

35 (>60 years, 27)

Upper arm

36 (>60 years, 36)

Elbow, flexion side

Pregnancy And Childbirth

Pregnancy And Childbirth

If Pregnancy Is Something That Frightens You, It's Time To Convert Your Fear Into Joy. Ready To Give Birth To A Child? Is The New Status Hitting Your State Of Mind? Are You Still Scared To Undergo All The Pain That Your Best Friend Underwent Just A Few Days Back? Not Convinced With The Answers Given By The Experts?

Get My Free Ebook


Post a comment