INTEGUMENTARY SYSTEM

ANATOMY AND PHYSIOLOGY

INTRODUCTION

• All living things are made of cells• Cells join together to make tissues• Tissues join together to form organs

Skin

• Skin is the principal organ of the integumentary system

• Skin is one of a group of anatomically simple but functionally important sheetlike structures called membranes

Membranes

Membranes

• A membrane is a thin, sheetlike structure with many important functions in the body

• Membranes cover and protect the body surface, line body cavities, and cover the inner surfaces of the hollow organs.

Two major categories of membranes

• Epithelial – composed of epithelial tissue and an underlying layer of specialized connective tissue

• Connective tissue membranes – composed exclusively of various types of connective tissue

Three types of epithelial membranes

–Cutaneous

–Serous

–Mucous

Cutaneous Membrane

Cutaneous Membrane

• Commonly called the skin• One of the largest and more

versatile organs of the body

Functions of Cutaneous Membrane

• Protective covering• Regulates body temperature• Prevents water loss• Houses sensory receptors• Synthesizes various biochemical• Excretes small qualities of waste

Serous Membranes

Serous Membranes• Found only on surfaces within closed

cavities• Composed of 2 layers of tissue – the

epithelial sheet and a thin layer of connective tissue

• Secrete serous fluid- watery fluid which lubricates the membranes surface

Serous Membranes

• Two types:–Parietal – lines the walls of a body cavity–Visceral – covers the surface of organs

found in the body cavities

Serous Membranes

• Pleura–Serous membranes that line the thoracic

cavity• Peritoneum

–Serous membranes that line the abdominal cavity

Mucous Membranes

Mucous Membranes

• Lines cavities and tubes that are open to the outside

• Consist of epithelial overlying a layer of loose connective tissue

• Specialized cells within a mucous membrane secrete mucus

Mucous Membrane

• Examples – linings of:–Respiratory–Digestive–Urinary, and–Reproductive tracts

Mucocutanous Junction

Mucocutanous Junction

The transitional area that serves as a point of “fusion” where the skin and mucous membranes meet

Connective Tissue Membranes

• Also called synovial membranes• Line the spaces between bones and

joints that move• Slick, smooth membranes that secrete

synovial fluid, which lubricates the ends of bones within the joint

• Reduce friction between bones

Cutaneous Membrane (Skin)

Composed of the following layers:• Epidermis-outer layer of skin• Dermis- middle layer of skin• Subcutaneous-innermost layer of

skin – thick layer of loose connective tissue and fat

Epidermis

• Tightly packed epithelial cells arranged in layers

• Inner – stratum germinativum • Outer – stratum corneum

Epidermis

• Inner layer – stratum germinativum – cells specialize to increase their ability to protect the tissues below them. This enables the skin to repair itself if it is injured. As the cells approach the surface, the cytoplasm is replaced by keratin, a protein which is tough and waterproof and protects the body

• Sometimes called the pigment layer because it is responsible for melanin production

Epidermis

• Outer layer – stratum corneum

• Keratin-filled cells are constantly pushed to the surface and “flake off”

• Millions of epithelial cells reproduce daily to replace the millions shed

Melanin

• Melanocytes are the cells within the pigment layer that produce melanin

• Melanin is a dark pigment that provides skin color

Melanin• Melanin absorbs light energy and protects

deeper cells from the ill effects of UV light.• Skin color is due largely to melanin• Color is mostly genetically determined but

can also be modified by sunlight exposure

Skin Color Abnormalities

• Cyanosis - bluish discoloration of the skin

• Jaundice - yellowish discoloration of the skin

• Erythemia - reddish discoloration

Skin Color Abnormalities

• Vitiligo – patchy areas of light skin resulting from the acquired loss of epidermal melanocytes. Most cases are genetic in origin.

• Albinism – hereditary condition, characterized by a partial or total lack of melanin. Affected individuals are prone to eye damage and sunburn

Dermis

• Binds the epidermis to the subcutaneous layer

• Contains blood vessels, hair follicles, nerve endings, sweat glands and nerve fibers

Dermis

• Upper region has parallel rows of peg like projections called dermal papillae

• Form the dermal-epidermal junction• Form groves and ridges that make

fingerprints• The pattern of these are unique in

every person

Dermis, cont.• Deeper area of dermis is collagen that

gives toughness to skin. • Elastic fibers are present• Makes skin stretchable and elastic• Wrinkles form as skin loses elasticity

Appendages

• Hair• Receptors• Nails• Skin glands

Appendages-Hair• Millions of small hairs cover the body• Follicles - present at birth, required for hair

growth• Newborns are covered with soft, fine hair called

lanugo• Areas of body that are hairless are lips, palms of

hands and soles of feet• Most visible on scalp, eyelids and eyebrows

Appendages-Hair

• Growth begins from a small cluster of cells called the papilla.

• Cells grow down into the dermis forming a small tube called the hair follicle

• The root is the part of the hair that we can’t see (under the skin)

• The shaft is the part of the hair we can see

Appendages-Hair• Alopecia is hair loss

• Arrector pili – involuntary muscle that contracts when we are frightened or cold, producing raised places called “goose bumps” or “goose pimples.”

Appendages-Receptors• Act as sense organs• Relay messages such as touch, pain, temperature and

pressure• Free nerve endings - respond to pain• Meissner’s corpuscles - located near the surface and

detects light touch• Ruffini’s corpuscles – located in dermal layer and

subcutaneous tissues of fingers, detect touch and pressure

• Pacinian corpuscle- deep in dermis and capable of detecting pressure

• Krause’s end bulb-responds to cold

Appendages-Nails

• Produced by cells in the epidermis• Form when epidermal cells fill with

keratin and become hard and platelike

Appendages-Nails• Nail body-visible part of the nail• Root-lies in a groove• Cuticle-groove and is hidden by a fold of

skin• Lunula-”little moon”, near the root• Nail bed- area beneath nail • Color pink due to abundant supply of blood

vessels seen through translucent nail bodies

Appendages-Skin Glands

• Sweat or Sudoriferous–Most numerous of skin glands–Two types: Eccrine and Apocrine

• Sebaceous–Oil-secreting glands

Appendages-Skin Glands

• Eccrine Sweat Glands–Numerous and widespread throughout

the body–Secrete watery liquid called perspiration

(sweat)–Sweat assists in the elimination of waste

products such as ammonia and uric acid

Appendages-Skin Glands

• Apocrine Sweat Glands–Found in axilla and in pigmented areas of

genitals–Large, secrete milky secretions–Produces odor that is caused by mixing

with skin bacteria–Enlarge and begin functioning at puberty

Appendages-Skin Glands• Sebaceous Glands

–Secrete oil for the hair and skin–Grow where hair grows–Tiny ducts open into hair follicles so that

their secretion, called sebum, can lubricate hair and skin.

–Sebum darkens to form blackheads–Acne vulgaris is the over secretion of

sebum

Disorders of Skin• Dermatosis-any disorder of the skin• Dermatitis-inflammation of the skin• Lesion-measurable variation from the

normal structure of a tissue–Distinguished by abnormal density, or

coloration–Discoloration usually occurs

Skin Lesions

ELEVATED• Papule• Plaque• Vesicle• Pustule• Crust• Wheal

FLAT• Macule

DEPRESSED• Excoriation

• Ulcer• Fissure

Skin Lesions

ELEVATED• Papule - warts• Plaque – can be caused by friction• Vesicle – non-genital herpes• Pustule – acne• Crust - scab• Wheal - hives

Skin Lesions

FLAT• Macule - freckles• Patch - vitiligo

DEPRESSED• Excoriation – scratches• Atrophy – stretch marks• Ulcer - bedsore• Fissure – athlete’s foot

Classification of Burns

• First-degree burns• Second-degree burns• Third-degree burns• Fourth-degree burns

• Third- and fourth-degree burns are both called full-thickness burns

Burns-Classifications

• First-degree burns-causes minor discomfort–Example-sunburn–Reddening of the skin–No blistering–Tissue damage is minimal

Burns-Classifications

• Second-Degree Burns–Involves deep epidermal layers–Causes injury to upper layers of dermis–Damages sweat glands, hair follicles and

sebaceous glands–Blisters, severe pain, generalized

swelling–Scarring is common

Burns-Classifications

• Third-Degree Burns–Complete destruction of the epidermis

and dermis–Tissue death extends to subcutaneous

layer–Insensitive to pain due to destruction of

nerve endings–Increased fluid loss

Burns-Classifications

• Fourth-Degree Burns–Full thickness burn that extends below the

subcutaneous layer to reach muscle or bone–Often result from electrical burns or exposure

to intense heat over time– Insensitive to pain due to destruction of nerve

endings– Increased fluid loss

Burns-Classifications

• Serious burns result in over 50,000 hospital admissions each year.

• Circulatory shock, fluid loss, respiratory injury, and infections are common complications.

• May require skin grafting or amputation of limbs

Estimating Body Surface Area• “Rule of Nines”-body is divided into

11 areas of 9%–Each arm is 9% for total of 18%–Head is 9%–Each leg is 18% for total of 36%–Torso is 18%–Back is 18%–Perineal area is 1%

Skin Infections

• Impetigo• Boils

Bacterial infections (streptococcal or staphylococcal)

Skin Infections

• Warts

Viral infections

Skin Infections

• Tinea – ringworm, jock itch, athlete’s foot

Fungal infections

Skin Infections

• Scabies – caused by the itch mite

Arthropod infestations

Skin Infections

• Decubitus ulcers – bedsores• Urticaria – hives (often caused

by allergic reaction)• Scleroderma – autoimmune

disease affecting blood vessels and connective tissues

• Psoriasis – plaques that remain on the skin for a long time

• Eczema – inflammation, caused by an underlying disease

Other skin disorders

Skin Cancers

• Squamous Cell Carcinoma• Basal Cell Carcinoma• Melanoma• Kaposi’s Sarcoma