Sweat Glands PDF

HUMHIS- SKIN |MIDTERM | Disturbance of sebum mainly cause of acne GLANDS OF SKIN Acne- inflammation of sebaceous...

HUMHIS- SKIN |MIDTERM | Disturbance of sebum mainly cause of acne GLANDS OF SKIN Acne- inflammation of sebaceous glands - The glands of skin are the sebaceous and sweat glands. - The oily secretion of sebaceous gland 2. Sweat Gland or Sudoriferous Gland keeps the skin smooth to prevent it from drying and the watery secretion of sweat found in the deeper part of dermis and gland keeps the skin surface cool, thereby is widely distributed. But it is absent in glans penis, inner surface of prepuce helps in maintaining body temperature. and margin of lip (cause it is thin skin) - SEBACEOUS - secrete oil to skin It is a simple coiled, tubular gland - Oil- keeps skin moisture prevent from whose duct usually opens on the drying epidermal surface. The part of the duct - Sweat glands- watery secretion present in the dermis is straight and is lined by stratified cuboidal epithelium, whereas the part that passes, through the epidermis is coiled 2 GLANDS OF SKIN and is limited by epidermal cells. (It has no lining of its own and is called 1. Sebaceous Gland acrosyringium.) found in the dermis of the skin and is a The secretory tubules are lined by simple acinar gland whose duct usually simple cuboidal epithelium and are opens into the hair follicle. But in bigger in size on cross section and certain regions, like glans penis, lightly stained, clitoris and lip, it opens directly onto whereas the ducts are smaller in size the epidermal surface. and darkly stained. Based on the mode of secretion, this There are two types of sweat glands gland is classified as holocrine gland. present in human beings, namely, The secretory acinus of the gland eccrine (merocrine) and apocrine. consists of a basal layer of undifferentiated flattened epithelial cells resting on a basement membrane and centrally placed rounded cells (sebocytes) filled with fat droplets. These rounded cells eventually become bigger and burst outpouring the secretion, sebum with remnants of nuclei and organelles. Sebum is an oily secretion having antibacterial and antifungal properties. It contains lipids and cholesterol and its esters (properties that has antibacterial and antifungal) The secretion of the gland is primarily Other Modified Glands of Skin controlled by testosterone in males and ovarian and adrenal androgens in 1. Modified apocrine sweat gland females. Mammary gland Ceruminous gland in external acoustic Sebum-originally from sebocytes meatus TRANSCRIBED BY: MAZI DUMP 1 LECTURE #1 | BSMLS – SKIN 2. Modified sebaceous gland Hair is found in all parts of the skin except Glands of Moll in eyelid palm, sole, lip, umbilicus, glans penis, Glands of Zeis in eyelid clitoris, labia minora and distal phalanx. Tarsal or Meibomian gland in eyelid Keratin - for hair, nails and skin Skin of fetus is covered by fine hair The Skin has various types of glands, each called lanugo (primary hair) which is with specific roles: shed at birth and is replaced by pale downy hair called vellus (secondary 1. Eccrine Sweat Glands - Common, hair). Vellus is retained in most of the found all over the body, release clear sweat for temperature regulation. regions of the body except scalp, face, 2. Apocrine Sweat Glands - Located in eyebrow, axilla and pubis, where it is hairy areas like armpits and genitals, replaced by coarse dark hair called produce thicker sweat leading to body terminal hair (influenced by sex odor when broken down by skin hormone). bacteria. Hair is not placed at right angles to the 3. Sebaceous Glands - Near hair follicles, surface but is set obliquely. The visible secrete oily sebum to lubricate skin and hair. projecting part of the hair is called shaft - Overactivity can cause acne. (scapus) and the invisible part 4. Mammary Glands - Specialized sweat embedded in the dermis, is called root glands in breasts produce milk for (radix / housed in the hair follicle). The breastfeeding. root of the hair is surrounded by a 5. Ceruminous Glands - In ear canals, tubular invagination of the epidermis create earwax (cerumen) to protect called hair follicle from which hair arises. against foreign particles and moisture. 6. Meibomian Glands- Found along Black- dominant color of hair eyelids, produce oily substance to prevent tear evaporation and keep eyes STRUCTURE OF HAIR moist. 7. Mucous Glands - In oral and nasal Hair consists of cuticle, cortex and membranes, secrete mucus to moisten medulla. and trap particles. 8. Modified Sweat Glands - Specialized Cuticle is the outer layer and is made of sweat glands in specific body regions single layer of flat scale-like cells that serve unique functions (e.g., ciliary overlap one another from below. glands in eyelashes). Cortex lies deep to the cuticle and is composed of several layers of elongated cells. Cortex forms the main APPENDAGES OF SKIN bulk of the hair. Medulla is found in the center and is - Appendages of skin include the hair and made of large vacuolated cells which nails which are made of dead scaly are often separated by air spaces. keratinized., cells derived from All the cells of the above layers of hair epidermis. contain hard keratin and melanin HAIR pigment granules Presence of hair in the skin is the characteristic feature of mammals. It is made of fused dead keratinized cells. TRANSCRIBED BY: MAZI DUMP 2 LECTURE #1 | BSMLS – SKIN Henle's layer, Huxley's layer, and the cuticle. The cuticle of the inner root sheath interlocks with the cuticle of the hair, helping to anchor the hair within the follicle. STRUCTURE OF HAIR FOLLICLE SOME INTERESTING FACTS ABOUT HAIR The hair follicle is a tubular structure in the epidermis that surrounds the hair's Straight hair are stronger than curly hair. root. Within the follicle, there's a deep, Hair do not grow continuously but have expanded part called the hair bulb, a growth cycle [they have period of consisting of pluripotent matrix cells growth (anagen phase) followed by a responsible for hair growth through period of rest (telogen phase)]. differentiation and keratinization. Hair growth is not affected by frequency Melanocytes in the hair bulb transfer of cutting or shaving. melanin granules to hair cells, giving hair Growth rate of hair is approximately its color. The hair bulb is indented by 1.5-2.2 mm per week. vascular connective tissue known as Hair grow faster between ages 26 and the hair papilla. 46 years. The hair follicle receives the duct of the Life span of hair varies from region to sebaceous gland and attaches to the region; in scalp as long as 4 years, in arrector pili muscle, a smooth muscle axilla as short as 4 months. below the sebaceous gland. Greying or whitening of hair is caused Contraction of this muscle causes hair to by either failure of melanocytes to form stand upright (goosebumps) in response pigment granules (congenital) or to cold or emotions. It also compresses appearance of small air bubbles among the sebaceous gland, releasing sebum. the cells of the cortex and medulla of The follicle's wall has two coats, hair. The reflection of light in the air including a connective tissue sheath. bubbles is responsible for the glistening or silvery appearance of white hair. The epithelial sheath of the hair follicle Baldness is caused by consists of several layers: - progressive atrophy of hair follicle with age 1. Glassy Membrane: This is a thickened - genetic factor basement membrane that separates - presence of androgenic the connective tissue sheath from the hormone. epithelial sheath. 2. Outer Epithelial Root Sheath: This layer is continuous with the stratum basale and stratum spinosum of the epidermis. 3. Inner Epithelial Root Sheath: This layer corresponds to the superficial layers of the epidermis and is found below the level of the sebaceous glands. It comprises three layers: TRANSCRIBED BY: MAZI DUMP 3 LECTURE #1 | BSMLS – SKIN NAIL Nail is a cornified plate of stratum 1. Meissner’s corpuscle corneum found on the dorsal surface of It is found in the dermal papillae of skin, the terminal part of fingers and toes. especially in thick skin. The inferior surface of nail rests on nail It is cylindrical in shape, oriented bed which corresponds to stratum perpendicular to the surface of the skin. basale and stratum spinosum of the Each corpuscle is composed of a stack epidermis. of flattened wedge-shaped modified The proximal part of nail is called nail Schwann cells (tactile cells) enclosed in root and is buried under a fold of skin a capsule with associated called eponychium. The skin beneath nonmyelinated nerve fibers which ramify the distal free end of the nail is known as among the stacked cells. hyponychium. It is extremely sensitive to touch and The nail grows distally by proliferation enables an individual to distinguish and differentiation of matrix cells of the between two points when they are nail bed found near the root. placed close together on the skin (two point tactile discrimination). Skin Receptors 2. Pacinian Corpuscle It is found in the dermis (also present in - Numerous nonencapsulated and ligaments, joint capsule, pleura, encapsulated receptors are found in the peritoneum, nipple and external skin and they respond to stimuli for genitalia). temperature, touch, pain and pressure. It is oval in shape and resembles a Thus, skin is the largest sense 1 organ sliced onion in a section. of the body. It consists of a central cylindrical core containing a naked axon surrounded by many concentric lamellae of flattened NONENCAPSULATED RECEPTORS epithelioid fibroblasts. It is sensitive to pressure and vibration. - are sensory nerve endings whose 3. Ruffini’s corpuscle terminations are not covered by It is fusiform in shape and is found in capsule. the dermis of the skin and joints. 1. Free Nerve Endings It consists of bundles of elongated They are found in epidermis and collagen fibers and fluid enclosed in a dermis. capsule with associated nerve fibers Free nerve endings in epidermis reach which ramify among the collagen up to stratum granulosum and are fibers. concerned with touch and pain it is sensitive to stretch. sensation. 2. Merkel’s corpuscle/disc It is found in stratum basale of the epidermis. Each corpuscle is composed of a free nerve ending that terminates as a disc-shaped expansion in relation to the Merkel's cell of the epidermis and is sensitive to touch. ENCAPSULATED RECEPTORS - In encapsulated receptors the termination of the nerve is covered by a capsule, not derived from nervous tissue. TRANSCRIBED BY: MAZI DUMP 4