Integumentary System II (Accessory Structures) Flashcards
What is hair composed of?
Dead keratinized cells
What is the structure of hair?
Inner medulla of soft keratin
Cortex of hard keratin
Outer cuticle of hard keratin
What part of the hair is innervated?
Papilla
Where are the stem cells found within hair?
The matrix within the bulb - these matrix stem cells divide and become keratinized, forming hair
Where are the melanocytes found within hair?
Matrix
Melanocytes here are more resistant to breakdown than in the skin therefore there is a consistent hair colour along the length of the hair shaft
What is the structure of the hair follicle?
Invagination of epidermis into dermis
Layers of epithelial cells surrounded by connective tissue
Glassy membrane = thickened basal lamina between external root sheath and connective tissue
What is the cycle of hair growth?
- Active phase: 2-5yrs of hair growth per day at 1/3mm per day
- Regression: Transition to resting phase
- Resting phase: Hair detaches from follicle (club hair)
- Reactivation: Follicle grows a new hair, sheds old hair
What are nails?
Dead, keratinized cells produced from epidermal stem cells located in epidermal fold around nail root, beneath the skin
What are sebaceous glands and follicles? What type of secretion do they have?
Secrete sebum (protects and softens keratin of hair and skin)
Holocrine secretion (cells burst to release secretions)
Sebaceous glands - secretions empty into hair follicle
Sebaceous follicles - larger than glands, empty onto epidermis
Both sebaceous glands and follicles have alveolar morphology (simple, branched, compound)
What are sweat glands? What type of secretion do they have?
Coiled tubes of epithelium with myoepithelia cells that contract to expel sweat (under ANS control)
Merocrine secretion for both types of sweat glands
What are the two types of sweat glands?
Merocrine (most common) - widespread, water secretions with ions, cool body and may excrete waste
Apocrine - deeper, armpits, groin, nipples, thicker secretion with potentially unpleasant odour
What are the three types of hair?
Vellus (fine hair)
Intermediate (coarse hair, e.g., on limbs)
Terminal (thick hair on head, eyelashes, eyebrows)
What is the eponychium?
Cuticle
Stratum corneum covering initial visible portion of nail
What is the shaft of hair?
Extends above skin surface
What is the root of hair?
Connects hair to follicle
