Chapter 4 Biosci

8/13/2019 Chapter 4 Biosci

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CHAPTER 4: BODY MEMBRANES

Body Membranes

-Cover surfaces

-Line body surfaces

-Form protective, often lubricating sheets around organs

TWO MAJOR GROUPS:

1. Epithelial Membranes

-include cutaneous (skin), mucous, serous

membranes

2. Connective Tissue Membranes

- represented by synovial membranes

A. EPITHELIAL MEMBRANES

- Also called covering and lining membranes

- Calling these membranes epithelial is inaccurate:

although they all contain an epithelial sheet,

it’s always combined w/ an underlying layer

of connective tissue

- simple organs

I. Cutaneous Membranes

-skin

-superficial epidermis: keratinizing stratified

squamous epithelium

-underlying dermis: mostly dense (fibrous)

connective tissue

-dry membrane: only membrane exposed to air

II. Mucous membrane

-epithelium resting on a loose connective tissue

membrane called: lamina propria

-lines all body cavities

that open to the exteriorrespiratory, digestive, urinary, reproductive

tracts

-cellular makeup varies

Most contain either stratified squamous

or simple columnar epithelium

-wet, moist membranes bathed in secretions or

urine

-often for absorption or secretion

-not all mucous membranes secrete mucous

Respiratory & digestive: secrete mucous

Urinary tract: no secretion of mucous

III. Serous membranes

-layer of simple squamous resting on a thin of

layer of areolar connective tissue

-line body cavities closed to the exterior

Except for dorsal body cavity, joint

cavities

-occur in pairs:

1. Parietal layer

- lines a specific portion of the wall of the

ventral body cavity, folds itself to form:

2. Visceral layer



-covers the outside of the organs in that

cavity

- Parietal-Visceral relationship may be viewed

as: pushing your fist (organ) into a limp

balloon partially filled with water

Part that clings closely to fist: visceralserosa lining organ’s external surface

Outer wall of balloon: parietal serosa

that lines walls of the cavity, fused to

cavity wall (never exposed)

- contains serous fluid

-thin, clear fluid secreted by parietal and

visceral membranes to separate them

-allows organs to slide easily across cavity

walls w/o friction (pumping heart, stomach

churning)

-specific names depend on locations:

1. Peritoneum

-lines abdominal cavity, covering its organs

2. Pleura

-surrounding lungs

3. Pericardium

-surrounding

B. CONNECTIVE TISSUE MEMBRANES

Synovial membranes

- composed of soft areolar connective tissue and

contain no epithelial cells at all

-line fibrous capsules surrounding joints:

1.provide smooth surface

2. secrete a lubricating fluid

- also line small sacs of connective tissue:

bursae and tendon sheaths = cushion organs moving

against each other during muscle activity

INTEGUMENTARY SYSTEM

-Skin, its derivatives (sweat and oil glands, hair, nails)

-Skin is also called the integument, meaning covering

Functions:

-NOT ALL PROTECTIVE

1. Keeps water and other precious molecules in the

body, keeps water out

-contains keratin that is cornified or hardened to

prevent water loss

2. Insulates and cushions deeper body organs and

protects entire body from:-Mechanical damage (bumps and cuts)

-Chemical damage (acids and bases)

-UV rays (sunlight)

-bacteria

3. Regulates heat loss from body surface

-capillary network and sweat glands

4. Acts as mini-excretory system



-urea, salts and water are lost when we sweat

5. Manufactures proteins to synthesize Vitamin D

6. Contain cutaneous sensory receptors

-touch, pain, pressure, temperature

*study table 4.1 page 114

Structure of the Skin:

Two kinds of tissue:

1. Epidermis

-stratified squamous epithelium capable of

keratinizing, or becoming hard

2.

Dermis

- mostly dense connective tissue

*epidermis and dermis are firmly connected

*blister

-result of burn or friction causing epidermis and

dermis to separate, allowing interstitial fluid to

accumulate in the cavity

3. Subcutaneous tissue

- deep to the dermis or hypodermis

-adipose tissue

-

not considered part of the skin, only anchors skin

to underlying organs

-serves as:

1. shock absorber

2. insulates deeper tissues from extreme

temperature

3. responsible for woman’s curves

I. Epidermis

-composed of 5 layers: stratum basale,

spinosum, granulosum, lucidum and corneum

- avascular

-most cells are keratinocytes, a fibrous proteinthat makes epidermis a tough protective layer

Stratum basale/ germinativum

-connected to the dermis

-epidermal cells that receive the most adequate

nourishment via diffusion from the dermis

-epidermal cells here continuously undergo cell

division, and millions of cells are produced daily

(stratum germinativum)

Stratum spinosum and stratum granulosum

-where daughter cells are pushed further, away

from the source of nutrition

-

cells become flatter, and increasingly full of

keratin

Stratum lucidum

-when cells finally die, they form this

-not present in all skin regions, only in regions

where skin is hairless and extra thick: palms and

soles

-has accumulating keratin that secretes a water-

repellent glycolipid into the extracellular



-point where di na talaga abot ng cells ang blood

supply and nutrients from dermis

Stratum corneum

-20 to 30 cell layers thick

-3/4 of the epidermal thickness

-contains cornified or horny cells Shinglelike dead cell remnants, completely

filled w/ keratin (tough protein, durable

overcoat for the body, protection from ext.

environment & water loss, resist biological,

chemical and physical assaults)

-rubs and flakes off slowly and steadily (18 kg/ 40 lb

in a lifetime)food source for dust mites

-replaced by cells produced by basale cells (new

epidermis every 25-45 days)

Melanin

-pigment that ranges from yellow-brown-black

-produced by special spider-shaped cells called

melanocytes (found in basale)

-when skin is exposed to sunlight, melanocytes are

stimulated to produce more melanin (tanning)

-As melanocytes produce melanin, membrane-

bound granules are accumulated within them

(melanosomes)these granules move to the ends

of the spidery arms of the melanocytestaken up

by keratinocytesInside keratinocytes, melanin

forms pigment umbrella over the superficial side of

the nuclei that shields DNA from damaging effects

of UV rays

-freckles and moles are seen where melanin is

concentrated in one spot

II. Dermis-“hide”

-strong, stretchy envelope that helps hold the body

together

-made up of dense fibrous connective tissue

-vary in thickness like epidermis

Two regions:

1. Papillary layer

- upper dermal region, uneven

-contains dermal papillae

peglike projections from superior surface

indent epidermis

has capillary loops that furnish nutrients to

epidermis

house pain receptors (free nerve endings)

and touch receptors (meissner’s)

increase friction and gripping ability (looped

and whorled ridges on palms and soles)

Papillary patterns are genetically

predetermined: fingerprints (identifying

films of sweat)

2. Reticular layer



-deepest skin layer

-contains blood vessels, sweat, oil glands and pressure

receptors (pacinian)

-phagocytes are found here and throughout dermis

-collagen and elastic fibers:

Collagen: toughness of dermis; attract and bindwater to hydrate skin

Elastic: elasticity while young

-abundantly supplied with blood vessels: to maintain

body temperature homeostasis

When temp. is high, capillaries of dermis

become engorged w/ heated blood

When temp. is cool, blood bypasses the dermis

capillaries temporarily, to allow internal temp.

to stay high

SKIN COLOR

3 pigments:

1. Melanin- yellow, reddish, brown or black

2. Carotene- deposited in corneum and subcutaneous

tissue, yellow-orange

3. Oxygen-rich hemoglobin- in red blood cells

*Emotions also influence skin color

Disease states:

1. Redness or erythema: embarrassment (fever),

hypertension, inflammation or allergy

2. Pallor or blanching: pale (fear, anger), anemia, low

blood pressure or impaired blood flow

3. Jaundice: usually signifies a liver disorder in w/c

excess bile pigments are absorbed into the blood &

deposited in body tissues

4. Bruises or black and blue marks: sites where blood

has escaped from circulation and clotted in tissue

spaces (hematomas); may signify deficiency in Vit. Cor hemophilia (bleeder’s disease)

Appendages of the Skin

-arise from the epidermis, maintains unique role body

homeostasis

I. Cutaneous Glands

-all exocrine glands that release secretions to the

skin surface via ducts

-pushed into deeper skin regions from basale, and

resides in dermis

Two groups:

A. Sebaceous glands

-oil glands

-found all over skin except palm and sole

-ducts empty into a hair follicle, but some open

directly onto the skin surface

-sebum

-product of the sebaceous glands

-mixture of oily substances and

fragmented cells

-lubricant that keeps the skin soft and

moist



-prevents hair from becoming brittle

-contains chemicals that kill bacteria

-become very active during adolescence because

hormones are produced

B. Sweat Glands

-also called sudoriferous glands

-widely distributed in the skin

-

2.5 million glands per person

Two types:

I. Eccrine

-more numerous

-produce sweat

clear secretion that is

1. primarily water

2. salts (sodium chloride)

3. vitamin C

4. traces of metabolic wastes

(ammonia, urea, uric acid)

5. lactic acid (chemical that accumulates

during vigorous muscle activity)

sweat is acidic (ph 4 to 6)

which inhibits the growth of

bacteria

sweat reaches the skin

surface via a duct the opens

externally as a funnel shaped pore

- important for heat regulation

supplied w/ nerve endlngs that

cause them to secrete sweat

when external temperature or

body temp. is high

- it is possible to lose up to 7 L of water on a hot day

- if internal temp. changes more than a few degrees 37C or 98.2 F, life threatening changes occur in the

body

II. Apocrine Glands

-largely confined to the axillary, genital areas of

the body

-larger than eccrine glands, ducts empty into

hair follicles

-secretion

fatty acids and proteins + other substances

milky or yellowish in color

odorless, but when bacteria that live on

skin use its proteins and fats as source of

nutrients, it takes on an unpleasant odor

produced continuously

- begin to function under the influence of

androgens (male sex hormones)

- play a minimal role in thermoregulation

- precise function: not known yet

- activated by nerve fibers during

pain/stress/sexual foreplay



C. Hair and hair follicles

-serves minor protective functions

I. Hair

-produced by hair follicle (flexile epithelial

structure)-root

Part of hair enclosed in the follicle

- shaft

Part projecting from the surface of the

scalp or skin

Dead, almost entirely protein

-hair is formed by division of the well

nourished stratum basale epithelial cells in

the matrix (growth zone)

-medulla

Central core

-cortex

Surrounds medulla, bound by cuticle

-cuticle

Single layer of cells that overlap each

other like shingles on a roof

This arrangement allows to keep hairs

apart and keep them from matting

Most heavily keratinized region:

provides strength and helps inner hair

layers tightly compacted

Most subject to abrasion, “split ends”

-hair pigment

Made by melanocytes in the hair bulb

Varying types of melanin combine to produce hair

color

Hair types:

1. When hair shaft is oval-hair is smooth and silky, person has wavy hair

2. When hair shaft is flat and ribbonlike

-hair is curly or kinky

3. When hair shaft perfectly round

-hair is straight and tends to be course

-hair is found everywhere except:

1. palm and sole

2. nipples

3. lips

-hairs are among the fastest growing tissues of the

body

-hormones account for the development of hairy

regions: scalp, pubic, axillary areas

II. Hair follicles

- Compound structures

- Inner epidermal sheath

Composed of epithelial tissue and forms the

hair

- Outer dermal sheath

Dermal connective tissue



Supplies blood vessels to the epidermal

portion and reinforces it

Nippelike papilla provides blood supply to

matrix in the hair bulb

- Arrector pili

-connect each side of the hair follicle to the dermaltissue

-when these muscles contract, hair is pulled upright

dimpling the skin surface w/ goose bumps

-hair raising phenomenon is not very useful to

humans

D. NAILS

Nail

-scale like modification of the epidermis that

corresponds to the hoof or claw of other

animals

-has a free edge, a body (visible portion), and

root (embedded in the skin)

-borders of the nail are overlapped by skin folds

called nail folds

-cuticle

Thick proximal nail fold

-nail bed

Stratum basale of the epidermis extends

beneath the nail

-nail matrix

Thickened proximal area of the nail bed

Responsible for nail growth

- As nail cells are produced by matrix, they become

heavily keratinized and die

- Nails are transparent and nearly colorless, but look

pink because of the blood supply in the underlying

dermis

Exception: lunula (white crescent)= lowblood supply due to thick underlying skin

Homeostatic Imbalances of Skin

- The skin can develop over 1000 different ailments

I. Infections and Allergies

A. Athelete’s foot

-itchy, red, peeling condition of the skin

between toes, resulting from fungus

infection

-tinea pedis

B. Boils and carbuncles

-inflammation of hair follicles and sebaceous

glands

-common in the dorsal neck

-Carbuncles: composite boils typically caused

by infection: staphylococcus aureus

C. Cold sores

-small fluid filled blisters that itch and sting

caused by herpes simplex infection



-localizes in the cutaneous nerve until

activated by emotional upset, fever or UV

rays

-usually occur around the lips and oral

mucosa of mouth

D. Contact dermatitis

-itching, redness and swelling of the skin,

progressing to blistering

-caused by exposure of the skin to chemicals

E. Impetigo

-pink, water-filled raised lesions that develop

a yellow crust and rupture

-highly contagious staphylococcus infection

-common among elementary school-aged

children

F. Psoriasis

-chronic

-overproduction of skin cells that result in

reddened epidermal lesions covered w/ dry,

silvery scales that itch, burn, crack and bleed

-when sever, may be disfiguring

-also believed to be an autoimmune disorder

in w/c immune system attacks a person’s

own tissues

attacks are triggered by trauma, infection,

hormonal changes or stress

II. Burns

-skin is only as thick as a paper towel

Burn

-is tissue damage and cell death caused by

intense heat, electricity, UV rays or certain

chemicals

When skin is burned and its cells destroyed:

1. The body loses its precious supply of fluids

containing proteins and electrolytes as these

seep from the burned surfaces

2. Dehydration and electrolyte imbalance follow

and lead to shutdown of kidneys and circulatory

shock (inadequate circulation of blood caused by

low blood volume)

3. Later, infection becomes the most impt.

Threat and the leading cause of death (burned

skin is only sterile up to 24 hours; and the

patient’s immune system becomes depressed

w/in 1-2 days after severe burns)

RULE OF NINES

-volume of fluid lost can be estimated directly by

determining how much of the body surface is

burned

-divides the body in 11 areas, each accounting for

9% of total body surface area+ 1% in genitals



Classification of Burns:

1. First degree burns

-only the epidermis is damaged

-temporary discomfort

-not usually serious and generally heal in 2-3 dayswithout attention

-sunburn

2. Second-degree burn

-injury to epidermis and upper region of dermis

-skin is red and painful, blisters appear

-regeneration can occur

-no permanent scar result if care is taken to prevent

infection

*first and second degree burns- partial-thickness

burns

3. Third degree burns

-destroy the entire thickness of the skin, so these

burns are also called full thickness burns

-burned area appears blanched or blackened

-not painful (destroyed nerve endings)

-regeneration is not possible, skin grafting must be

done

BURNS ARE CRITICAL WHEN:

1. Over 25% of the body has second degree burns

2. Over 10% of the body has third degree burns

3. Third degree burns on face, hands or feet

*Facial burns dangerous because: burns in

respiratory passage can cause suffocation & joint injuries

because scar tissue can severely limit joint mobility

Skin Cancer

-Most skin neoplasms are benign and do not spread

(metastasize) to other body areas

-single most common type of cancer

-causes: infections, chemicals, physical trauma

A. Basal Cell Carcinoma

-least malignant and most common type of skin

cancer

-cells of stratum basale are altered that they cannot

form keratin

-cancer cells proliferate, invading dermis and

subcutaneous tissue

-cancer lesions: occur most often on sun-exposed

areas and appear as shiny dome shaped

noduleslater develop into an ulcer w/ a pearly

beaded edge

- slow growing, metastasis seldom occurs before its

noticed

-cure: lesion is removed surgically

B. Squamous Cell Carcinoma



-arises from cells of stratum spinosum

-lesion appears scaly, reddened papule (small round

elevation) forms an ulcer w/ a firm raised border

-appears mostly on scalp, ears, dorsum of hands,

lower lip

-grows rapidly and metastasizes to adjacent lymphnodes if not removed

-sun-induced

-when caught early and removed surgically/ by

radiation therapy, chance of full cure is good

C. Malignant Melanoma

-cancer of melanocytes

-5% of skin cancers

-often deadly

-can begin wherever there is a pigment, some

develop from pigmented moles

-arises from accumulated DNA damage in a skin cell,

appears like a spreading brown-black patch

-metastasizes fast to surrounding lymph and blood

vessels

-chance for survival 50%, early detection helps

-sunbathing, tanning

ABCD RULE:

1) Asymmetry- 2 sides of pigmented mole don’t

match

2) Border irregularity- borders of the lesion are not

smooth, exhibit indentations

3) Color-areas of different colors (blacks, browns,

tans, blues, reds)

4) Diameter- spot is larger than 6 mm in diameter

5) Elevation-above skin surface

Therapy: wide surgical excision w/ immunotherapy

DEVELOPMENTAL ASPECTS:

Lanugo

-during 5th

and 6th

months of fetal development, a

soon to be born infant is covered w/ this

-downy type of hair

-shed by birth

Vernix caseosa

-white, cheesy looking substance

-produced by sebaceous glands

-protects baby’s skin while floating in water-filled

sac inside mother

Newborn’s skin is very thin, and blood vessels are

easily seen through it

Milia

-accumulations in the sebaceous glands

-small white spots on nose and forehead

-disappear by 3rd

week of birth

As baby grows, skin becomes thicker and moist,

more subcutaneous fat is deposited



During adolescence, hair and skin become more oily

as sebaceous glands are activated= acne may appear

Acne subsides in early adulthood, and skin reaches

its optimal appearance during 20s or 30s

Dermatitis or skin inflammations become more

common as visible changes are seen in our skin

During old age, amount of subcutaneous tissue

decreasesintolerance to cold

Skin also becomes drier, may become itchy andbothersome

Thinning of skin, makes it more susceptible to

bruising and other types of injuries

Decreased elasticity of skin + loss of subcutaneous

fat= allows bags to form under eyes and our jowls

begin to sag

Loss of elasticity: speeded up by smoking and

sunlight

By 50, number of hair follicles has dropped by 1/3

and continues to decline hair thinning and alopecia

(degree of baldness)

Male pattern baldness- maraming lalaki ang

nakakalbo

A bald man is not really hairless, the hairs are

colorless and tiny (vellus hairs) since the follicleshave begun to degenerate

Graying hair- genetically controlled by a “delayed

action gene” (once gene takes effect, the production

of melanin deposited decreases or is entirely absent)

Chapter 4 Biosci

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