a + p accessory structures

hair

keratinized squamous epithelial cells

• columns - very similar to epidermal level of skin

found on most body surfaces

• for humans in various amounts - regions of thick skin don’t have hair

hair structure

• shaft

• root

• follicle

• hair matrix

hair shaft

above skin surface

cells that make up each shaft are dead keratinous cells

hair root

remainder of hair within skin - embedded within skin

living keratinocytes dividing currently

hair follicle

layer of epidermal tissue anchoring root into dermis

the inner root sheath and outer root sheath make up the follicle

each individual hair is embedded into the follicle

• it holds the hair in place

hair matrix

region of diving cells adjacent to papilla

• newer cells in the matrix push old cells up - how hair gros

active cell division taking place

arrector pili

attached to hair follicle on one side and dermal papillae on the other

smooth muscle

contract to cause piloerection

piloerection

raising of hair that causes goosebumps

when the arrector pili contracts, it causes tension of the hair follicle and the skin, which causing hair to then stand up and produce goosebumps

for other animals, piloerection allows them to appear larger and more threatening

the arrector pili is used for ______________ and ____________ in non-human mammals

thermoregulation, defense

when hairs stand up, it can trap a layer of air, providing insulation and heat retention

hair shaft structure:

• medulla

• cortex

• cuticle

medulla

core of large keratinocytes and loosely arranged cells

contains soft keratin

soft keratin

found in the epidermis and medulla of hair shaft

• provides durability while allowing tissue to remain flexible

cortex

several layers of compact keratinocytes

• gives our hair volume

contains hard keratin

site of pigmentation (hair color)

hard keratin

found in cortex and cuticle of hair shaft

• more durable - doesn’t shed the hard keratin keratinocytes like soft keratin does

  • good because our hair strands would quickly break down if it shed

  • protects underlying layers as well

cuticle

single layer of overlapping cells

• keeps hair from sticking to each other

most highly keratinized region

• hard keratin

split ends

damage to the cuticle and exposes underlying layers

• cortex and medulla no longer protected

splitting or fraying of hair shaft

• usually the ends - because of the way our hair grows, the ends of our hair are the weakest/most fragile

  • the ends are the oldest parts of our hair, therefore have experienced the most damage from environmental factors (UV, wind, mechanical stress)

can split ends be repaired?

no - all of the cells in the shaft are dead so they can’t repair themselves - the structure can’t be repaired

types of hair

• lanugo

• vellus

• terminal

lanugo hair

very fine, unpigmented fetal hair

insulative purpose for developing baby in the uterus environment

• falls of after birth and is replaced by vellus hair

vellus hair

fine, thin body hair

female bodies usually have more vellus hair than terminal hair

terminal hair

longer, coarser, heavily pigmented hair

eyebrows, eyelashes, and scalp hair at all ages

axillary and pubic hair (after puberty)

adult males: facial hair, some hair of trunk and limbs

terminal hair replaces ___% of vellus hair in males and ___% in women

90, 30

texture of terminal hair

related to cross-sectional shape of hair follicle - it affects the shape the hair is (straight, wavy, curly) and the texture

• flatter follicles grow curlier hair

• when the hair grows from a relatively flat follicle, the hair will bend and be curlier

color of terminal hair

pigment granules in cells of cortex - result in different pigments providing color to shaft - melanin!

• eumelanin or pheomelanin

• more melanin = darker hair

gray and white hair have little or no melanin

shades of hair depend on the ratio of _________ and __________

eumelanin and pheomelanin

hair growth cycle

1. anagen

2. catagen

3. telogen

4. repeat

anagen

growth phase

• active cell division - push old cells up causing hair growth

• 90% of scalp follicles are in anagen phase and remain for years

• nourishment of hair follicles via blood supply enables hair growth

catagen

transition phase

• see a decrease in cell division - hair growth slows down

• hair follicle detaches from nourishing blood supply

telogen

resting phase

• few months where no new growth is occurring

• the hair is still attached on the follicles but the cells that are attached to them are starting to die off

  • hair is very easy to detach at this point

  • hair sheds 50-100 hairs everyday and then are replaced

terminal hair growth: scalp

in anagen for ~ 6 years - cell division is quick on the scalp

higher mitotic rate

terminal hair growth: eyebrows/lashes

in anagen for ~ 30 days - much shorter time, low potential for hair growth

lower mitotic rate

• only capable of growing a few mm long

terminal hair growth

the duration of phases determines the rate of growth and how hair can grow in that area

growth slows ~ 50 years of age

• hairs shed faster than new ones grow → thin hair, baldness

• as we age, mitotic rate decreases

nails

• modified epidermis

• nail plate

• nail bed

• nail matrix

• function in protection and object manipulation (holding and grabbing)

nail modified epidermis

• hard keratin - our nails are much more durable and stronger than the skin because of the hard keratin (protection)

• no melanocytes - translucent

nail plate

• body: external

• root: internal

nail bed

epidermis underlying nail plate

nail matrix

site of nail growth

• active cell division is similar to hair - new cells push old cells - mitotic rate is faster in fingers than toes

glands of the integumentary system

groups of modified epithelial cells - modified to perform different functions

• located in the dermis

• exocrine

• sweat and sebaceous

• endocrine

exocrine glands

release non-hormonal secretions

• released onto surface of the skin or onto hair follicles

endocrine glands

hormonal secretion into circulatory system

sweat glands: eccrine

eccrine: most numerous type of gland

abundant throughout the body

allows for evaporative cooling

• produces a water sweat that gets deposited onto the skin - cools body down (thermoregulation) - it absorbs excess body heat

sweat secreted onto skin surface via ducts

sweat from eccrine sweat gland

• 99% water

• contains solutes, wastes, antibacterial compounds

• slightly acidic

sweat glands: apocrine

only in axillary/genital regions

sweat secreted into hair follicles through ducts that lead to hair follicles

• revealed along shaft of hair

sweat from apocrine sweat gland

mostly made of water but higher % of fatty acids and proteins

• when bacteria break them down, it causes body odor - bacterial activity produces odor

sweat secreted by apocrine glands are nonfunctional until _________

puberty

modified sweat glands: ceruminous

found in lining of ear canal

secrete cerumen (ear wax)

cerumen

sebum (oil) and dead epithelial cells provide lubrication for ear

• protection: very sticky and prevents foreign particles from entering

provides lubrication and protection

modified sweat glands: mammary

found within adipose tissue of breasts

secrete/produce milk - mostly water and proteins, lipids, carbohydrates, hormones, and antibodies, to nourish infant in postpartum lactation period

present in males and females

mammary sweat glands only develop during _________ and __________

pregnancy, lactation

function requires specific hormonal environment during pregnancy and lactation - mostly nonfunctional, especially for males

sebaceous glands

produces oil throughout the body but most numerous on the face and scalp

secretes into hair follicles

secretes sebum (oil)

sebaceous glands are largely _______ until ________

inactive, puberty

sebum from sebaceous glands

lubricates/waterproofs skin and hair

• prevents it from becoming overly dry and maintains hydration

bactericidal properties

• protect from being colonized by bacteria