The Integumentary System

Skin Appendages

Skin AppendagesSkin AppendagesA skin appendage is defined as anything that assists the skin with its function– expelled cells from the epidermis– modifications of the epidermis– appendages in the dermis and subcutaneous

layer develop from special cells that migrate there during embryological development

• glands• nerves• nails• hair

Skin AppendagesSkin AppendagesGlands

• ceruminous

• sebaceous

• sweat

Skin AppendagesSkin Appendagesceruminous glands

• in skin lining ear canal

• specific type of apocrine gland

apocrine – consisting of pinched-off cytoplasm, including some cell membrane

• produces a waxy secretion = cerumen (ear wax)

• openings surrounded by small hairs

Skin AppendagesSkin Appendagessebaceous glands• holocrine gland

holocrine – secretes whole dead cellsThe cells secreted by sebaceous glands

produce and store an abundance of fat along with their membrane organelles

1) cells secreted into gland ducts2) cells burst open3) fats released onto surface of skin as oily

secretion = sebum

Skin Appendages• sebaceous glands secrete sebum into hair

folicles (hair bulbs)

• sebum then moves to the surface of the skin along the hair

• when the gland becomes clogged, sebum backs up

Skin Appendagessweat glands – 2 types

1) apocrine sweat glands

2) eccrine sweat glands

apocrine sweat glands• secrete odorous material into hair folicles

of:– armpits– navel– groin region– areolae

• secretion contains pheromones– play a role in courtship and social behavior

apocrine sweat glandsapocrine sweat glands• secretions of apocrine sweat glands are

readily broken down by bacteria → body odors

• these glands are inactive until puberty

• there is decreased activity in these glands in the elderly

Skin Appendageseccrine sweat glands

• mostly on the skin of:– armpits– forehead– palms– soles

• sweat production varies from individual to individual – gland activity, concentration, and distribution are determined by genetics

eccrine sweat glandseccrine sweat glands

sweat is primarily water with various concentrations of salts, organic compounds, and wastes (like urea)

eccrine sweat glandseccrine sweat glands

• microbes feed of the nutrients in eccrine sweat → body odors

Skin Appendages

nerves

• sensory receptors allow the skin to communicate information from the environment to the body

• sensory receptors are found in all layers of skin – mostly the innermost regions and fascia

Nerves in the Skin

free nerve endings

• numerous

• in the inner part of the epidermis

• pain-sensing

• detect chemicals associated with tissue damage and bleeding → registers as pain

Nerves in the Skin

Merkel cells

• small numbers in the stratum germinativum

• sensitive to gentle physical sensations

• found mostly in areas having special sensitivity like fingertips

Nerves in the Skin

Meissner’s corpuscles (tactile corpuscles)

• upper regions of dermis, in the dermal papillae

• respond to touch

• surrounded by an elongated, club shaped pile of connective tissues

• pressure on the Meissner’s corpuscles compresses the connective tissue, causing the nerve to respond

Nerves in the Skin

Pacinian corpuscles (lamellated corpuscles)

• found in deeper areas of the subcutaneous layer (hypodermis)

• respond to hard pressure, including vibration

• shaped like onions

Nerves in the Skin

Ruffini receptors

• also in the dermal papillae

• detect pressure or constant touch

Nerves in the Skin

Krause end bulbs

• branched throughout the dermis

• sensitive touch receptors

• mostly in the mucous membranes of the mouth

Skin Appendages

Nails– just keratin secretions

• each nail grows forward from a nail root– in the skin-nail fold

• nails grow as long as nail root and skin-nail fold are not severely damaged

Nails

Nail Growth

• keratocytes at the base of the nail move up to the surface

• cells closests to the surface:1) die

2) flatten out

3) press tightly together

4) disentegrate into the nail body (matrix)

Nails

• as cells in the matrix accumululate, they continuosly push the nail forward

Nail Parts• lunula – white part at the base of the nail

body• nail plate – pink portion underneath the

nail body• cuticle – outgrowth of upper part of skin-

nail plateaverage growth is 1/8 inch per month

Skin AppendagesHair

• considered a modified stratum corneum, formed by an inward protrusion of the epidermis = hair follicle (hair bulb)

• base of the follicle, in the subcutaneous layer, is called a hair papilla– supplied by small blood vessels– connected to a nerve

Hair• The dead, hardened cells protruding from

the infold of the skin which formed the follicle become the main part of hair – the hair shaft

• most hairs have 2 layers

1) cortex– dead, densely packed cells full of keratin

2) medulla– inner layer– loosely arranged cells

Hair• larger hairs have a dried surface = cuticle

• the keratin in the cells gives the hair a yellowish color

hair color

• melanocytes at the base of the hair secrete red, brown, and black pigments

• differences in color due to amount and location of melanin in the cortex and medulla

• controlled by genetics

HairHair cycle = the mitosis cycles that the hair follicle undergoes to produce a length of hair

• newly formed hair cells move up the follicle

• newer cells formed beneath

• cells dry out, fill with keratin, harden, and die

HairIn addition to sebaceous glands, hair follicles also have an arrector pili muscle– band of smooth muscle– holds the hair erect

In fine body hair, vellus hair, the arrector pili muscle helps the hair to act like a sensitive touch receptor

Use of Hair Shaft Cells in Forensics• Hair cells capture many types of chemicals

that pass through the blood

• Any drug or poison that has been in a person’s body can be found in hair

• Drug-testing can be performed on the metabolic products found in the living cells at the base of the hair follicle– morphine found in hair of mummies– residues of drug breakdown found in older

cells

Use of Hair Shaft Cells in Forensics• DNA and mitochondria can be removed

from hair cells → genetic testing– genetic testing on hair from bodies buried for

hundreds of years

diagram of a sebaceous gland

cross section slide of skin showing sebaceous gland

A) normal sebaceous gland

B) dirt clogs pore

C) sebum gets trapped

D) bacteria begins to grow

E) acne develops