Download Physiology Ch 4

Chapter 4
Skin and Body Membranes
body membranes
- cover surfaces
- line body cavities
- form protective sheets around organs
- 2 groups:
epithelial membranes
connective tissue membranes
epithelial membranes - covering and lining membranes
- consist of an epithelial sheet attached to an underlying layer of connective tissue
- include:
cutaneous membrane (skin)
mucous membranes
serous membranes
cutaneous membrane - skin
- dry membrane
- consists of: epidermis
dermis
- superficial
- stratified squamous epithelium
- under epidermis
- mostly dense fibrous connective tissue
mucous membranes
- AKA mucosa
- wet membranes
- line all body cavities open to the exterior
- composed of epithelium resting on a loose connective tissue
membrane (lamina propria)
- most contain stratified squamous (mouth, esophagus) or simple columnar
(rest of digestive tract)
- many secrete mucous but not all (urinary tract)
serous membranes
- AKA serosa
- line body cavities closed to the exterior
- composed of simple squamous epithelium resting on a thin layer of areolar CT
- occur in pairs:
parietal layer - lines part of the wall of the ventral body cavity
- folds in on itself to form visceral layer
visceral layer - covers the outside of the organs in that cavity
- serous fluid - thin fluid found between parietal & visceral layers
- serous membrane lining abdominal cavity
- serous membrane surrounding the lungs
- serous membrane surrounding the heart
peritoneum
pleura
pericardium
connective tissue membranes - synovial membranes
- composed of soft areolar CT
- line joints (provide a smooth surface, secrete a lubricating fluid
- also line bursae (small sacs of CT), and tubelike tendon sheaths
Integumentary System (Skin)
integumentary system - consists of the cutaneous membrane (skin), sweat & oil glands, hair and nails
basic skin functions:
external body covering
- keeps water and essential molecules inside the body
- keeps water and other things (bacteria, etc.) out
insulates & cushions deeper organs
protects body from:
mechanical damage (scrapes, cuts)
chemical damage (acids, bases)
thermal damage (heat, cold)
ultraviolet radiation (in sunlight)
regulate heat loss (capillaries and sweat glands)
excretion (urea, water, and salts are lost in sweat)
makes vitamin D
sense touch, temperature, pressure and pain (nerve receptors)
keratin - protein found in uppermost skin layer
- hardens the skin’s surface to prevent water loss
- some skin is said to be cornified or keratinized
skin structure
epidermis
dermis
epidermis
dermis
- stratified squamous epithelium
- may become keratinized
- no blood supply (avascular)
- firmly connected to the dermis
- made mostly of dense connective tissue
blister - results when the epidermis separates from the dermis due to a burn or friction
- filled with interstitial fluid
subcutaneous tissue
- AKA hypodermis
- mostly adipose tissue
- attaches skin to underlying organs
- shock absorber and insulator
epidermis
keratinocytes - most of the cells in the epidermis
- produce keratin (fibrous protein that makes epidermis tough)
5 layers of the epidermis
stratum basale - deepest layer
- cells receive nourishment by diffusion from the dermis
- cells constantly divide (millions of new cells a day) and move to upper layers
- as cells move upward they become flatter, full of keratin, and eventually die
stratum spinosum
stratum granulosum
stratum lucidum
- only found where skin is hairless and extra thick (palms, soles)
stratum corneum
- outermost layer
- contained cornified cells (shinglelike dead cells filled with keratin)
- provide a durable overcoat for the body
- slowly flakes off
melanocytes
- cells found mainly in the stratum basale
- produces a pigment called melanin
- stimulated by sunlight to produce more melanin (tanning)
freckles, moles
dermis
2 layers:
- melanin concentrated in 1 spot
papillary layer - upper dermal region
- has dermal papillae - fingerlike projections into epidermis
- many have capillaries which supply epidermis
- some have pain receptors (free nerve endings)
- some have touch receptors (Meissner’s corpuscles)
reticular layer - deepest skin layer
- contains blood vessels, sweat & oil glands and deep pressure
receptors (Pacinian corpuscles)
dermis - collagen and elastic fibers found throughout
- elastic fibers decrease with age
- many blood vessels (keep body temperature stable)
- many nerves
skin color
due to:
melanin (how much and what kind  yellow, brown, or black)
carotene
- orange-yellow pigment found in carrots and other vegetables
- deposited in dermis and subcutaneous tissue
hemoglobin - pigment in red blood cells (makes skin appear pink in light-skinned people)
erythema
- skin redness
- may indicate embarrassment (blushing), fever, hypertension, inflammation, or allergy
pallor
- paleness
- may occur with stress (fear, anger)
- may indicate anemia or low blood pressure
jaundice
- yellow skin tone
- usually due to a liver disorder (excess bile pigments are deposited in tissues)
bruises
- black and blue marks
- blood has escaped blood vessels and clotted in tissue spaces
hematoma
- clotted mass of blood
cutaneous glands
- all are exocrine
- release secretions to skin surface
- sebaceous and sweat glands
sebaceous glands
- oil glands
- found all over the body (except palms and soles)
- ducts usually empty into a hair follicle
sebum - product of sebaceous gland
- mixture of oily substances and cell fragments
- keeps skin soft and moist; keeps hair from becoming brittle
acne - infection of sebaceous glands
sweat glands - 2 types:
eccrine and apocrine
eccrine glands - found all over the body
- ducts empty onto skin surface
- produce sweat when external temperature or body temperature is high
- sweat evaporates from the skin surface carrying body heat with it
sweat - mostly water, some salts, etc
- acidic (inhibits bacterial growth)
apocrine glands
- found mainly in axillary and genital regions
- ducts empty into hair follicles
- sweat here contains fatty acids and proteins
- bacteria use the fats and proteins for nutrition
- produce musky odor
- begin to function when exposed to male sex hormones (androgens)
during puberty
hair
functions of the hair: protects head against bumps
shields eyes (eyelashes)
keeps foreign particles out of respiratory tract (nose hairs)
hair follicle
hair
- structure that produces a hair
- epidermal sheath: inner layer of follicle
composed of epithelial tissue
forms hair
- dermal sheath:
outer layer of follicle
composed of CT
supplies blood vessels to epidermal sheath
- almost entirely protein (keratin)
root - part of the hair enclosed in the follicle
shaft - part of the hair projecting from the skin
- pigment comes from melanocytes in follicle
- found all over the body except palms, soles, lips, and nipples
- hormones account for development of hairy regions
arrector pili
- smooth muscle
- connect sides of follicle to dermal tissue
- contract to form “goose bumps”
alopecia
- baldness
nail
- modification of the epidermis
- each contains:
a free edge
a body (visible attached portion)
a root (embedded in skin)
- nail fold:
skin overlapping the nail  cuticle
- nail bed:
stratum basale extending under the nail
appears blue when O2 supply is low
- nail matrix: thickened part of nail bed
responsible for nail growth
produces nail cells which become heavily keratinized and die
- lunula:
crescent-shaped region of the nail over the matrix
athlete’s foot - AKA tinea pedis
- fungal infection of feet
- itching, red, peeling condition
boils and carbuncles - inflammation of hair follicles and sebaceous glands
- often caused by bacterial infection
cold sores
- small, fluid-filled blisters that itch and sting
- usually around lips and in mouth
- caused by a herpes virus
- virus stays dormant in a cutaneous nerve until activated by emotional upset,
fever, or UV rays
contact dermatitis
- itching, redness, and swelling of the skin; eventually blisters
- caused by contact with chemicals that caused allergies in sensitive people
(example: poison ivy)
impetigo
- highly contagious bacterial infection common in children
- pink, water-filled raised lesions usually around mouth and nose
- develop a yellow crust
psoriasis
- red, dry, scaly lesions due to overproduction of skin cells
- chronic
- may be triggered by stress, infection or hormonal changed
whitehead
blackhead
acne
- duct of sebaceous gland blocked by sebum
- a whitehead’s accumulated material dries and darkens
- infection of sebaceous gland
burns - tissue damage and cell death caused by intense heat, electricity, UV rays, or chemicals (acids)
- serious burns can lead to life-threatening problems:
dehydration - body loses fluids, proteins, and electrolytes as they seep from the
burned surfaces
kidneys may shut down due to dehydration and electrolyte imbalance
circulatory shock
- inadequate blood circulation due to low blood volume
infection
- important threat later on
- leading cause of death in burn victims
rule of nines
- estimates how much of the body surface is burned
- divides body into 11 areas each represent 9% of the body’s surface plus 1 area
representing the last 1%
head
- 9%
right arm
- 9%
left arm
- 9%
anterior trunk
- 18%
posterior trunk
- 18%
anterior right leg
- 9%
posterior right leg
- 9%
anterior left leg
- 9%
posterior left leg
- 9%
genital region
-1%
100%
burn severity
first-degree burn
second-degree burn
third-degree burn
- partial-thickness burn
- epidermis is damaged (example: sunburn)
- area becomes red and swollen
- usually heal in 2-3 days
- partial-thickness burn
- epidermis and upper dermis is damaged
- skin becomes red and painful; blisters appear
- regeneration of epithelium can occur
- usually doesn’t scar if infection is prevented
- full-thickness burn
- destroys entire thickness of skin
- burn appears gray-white or blackened
- not painful since nerve endings are destroyed
- regeneration is not possible  skin grafts are necessary
critical burns: >25% of body has 2nd degree burns
>10% of body has 3rd degree burns
there are 3rd degree burns on face, hands, or feet
skin cancer
- most skin neoplasms are benign
- some are malignant (cancerous)
- most common type of cancer in humans (1 in 5 Americans will develop it)
- most important risk factor: UV radiation
basal cell carcinoma - most common skin cancer
- least malignant
- cells of stratum basale proliferate invading dermis and subcutaneous tissue
- slow-growing
- 99% cure rate
squamous cell carcinoma
- arises from cells of stratum spinosum
- scaly red bump gradually forms a shallow ulcer
- grows rapidly and metastasizes to lymph nodes if not removed
- if caught early, chance of complete cure is good
malignant melanoma - cancer of melanocytes
- 5% of skin cancers
- often deadly
- can occur anywhere but some develop from moles
- usually appears as a spreading brown to black patch
- metastasizes to lymph nodes and blood vessels
- 50% chance of survival
ABCD rule - used to recognize melanoma
(A) Asymmetry
- the 2 sides of the spot don’t match
(B) Border
- borders not smooth
(C) Color
- spot has areas of different colors
(D) Diameter
- spot is larger than 6mm in diameter