BIOH111 SN24 Lecture IntegumentarySystem · PDF filemelanocytes secrete it in secretory vesicles ... Accessory skin structures ... evaporation (perspiration)

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BIOH111

oCell Module

oTissue Module

o Integumentary system

oSkeletal system

oMuscle system

oNervous system

oEndocrine system


Textbook and required/recommended

readings

o Principles of anatomy and physiology. Tortora et al; 14th

edition: Chapter 5


BIOH111 – INTEGUMENTARY

SYSTEM MODULE

o Session 6 (Lectures 11 and 12) – Structure and

function of the skin and accessory structures

BIOH111Lectures 11 and 12

Structure of the skin and accessory

structures

Department of Bioscience

endeavour.edu.au


ObjectivesLecture 11:

Structure of skin

• Define and describe the structure of each skin layer

Accessory skin structures

• Define and describe the structure of each accessory skin structure

Lecture 12:

Functions of skin

• Define and describe the function the skin

Wound healing

• Describe process of the epidermal wound healing

• Describe the process of deep wound healing

• Compare epidermal and deep wound healing

Burns

• Describe types of burns and damages to the skin layer

• Describe method for measuring the extent of burns


FUNCTIONS OF

INTEGUMENTARY SYSTEMo Thermoregulation

o Blood reservoir

o Protection

o Cutaneous sensations

o Synthesis of Vitamin D

o Excretion


GENERAL ANATOMY

www.webmd.com

o Large organ composed of all 4

tissue types; 2m2 in area; 1-2 mm

thick; weight: 4.5 kg

o 3 layers:

1. Epidermis: superficial portion; composed of epithelial tissue

2. Dermis: deeper layer; primarily composed of connective tissue

3. Hypodermis (or subcutaneous layer): deepest layer; consists of areolar and adipose tissue; not part of the skin

http://www.webmd.com/beauty/wrinkles/cosmetic-procedures-overview-skin


EPIDERMIS

o Stratified squamous epithelium:

• avascular (contains no blood vessels)

• 4 types of cells divided into 5 distinct strata (layers)


CELLS OF EPIDERMIS1. Keratinocytes:

• produce keratin and contain lamellar

granules

• function: help protect the skin and

underlying tissue from heat, microbes,

and chemicals; release lipids (waterproof)

2. Melanocytes:

• produce pigment melanin

• function: contribute to skin colour and

absorb damaging ultraviolet (UV) light

3. Langerhans cells:

• derived from bone marrow

• function: participate in immune response

4. Merkel cells:

• contact tactile (Merkel) disc

• function: sensation of touch


LAYERS (STRATA) OF THE EPIDERMIS


STRATUM BASALE

(STRATUM GERMINATIVUM)

o Deepest single layer of epidermis

o Cells: Merkel cells, melanocytes, keratinocytes and stem cells

that divide repeatedly; cells attached to each other and to the

basement membrane by desmosomes and hemi-

desmosomes


STRATUM SPINOSUM

o Cells: mostly keratinocytes; some melanocytes; 8 to 10 cell

layers are held together by desmosomes

o Function: provides strength and flexibility to the skin

o Melanin is phagocytosed by keratinocytes after nearby

melanocytes secrete it in secretory vesicles


STRATUM GRANULOSUM

o Transition layer between the deeper, metabolically active

strata and the dead cells of the more superficial strata

o Cells: keratinocytes which contain lamellar granules (release

lipid that repels water) and dark-staining keratohyalin

granules (keratohyalin converts tonofilaments into keratin);

3-5 layers of flat dying cells that show nuclear degeneration


STRATUM LUCIDUM

o Present only in the fingers tips, palms of the hands, and soles

of the feet.

o Three to five layers of clear, flat, dead keratinocytes that

contain keratin precursor


STRATUM CORNEUM

o 25 to 30 layers of flat dead cells filled with keratin and

surrounded by lipids from lamellar granules; continuously shed

o Function: barrier to light, heat, water, chemicals and bacteria

o Callus: an abnormal thickening of the epidermis with constant

exposure to friction to this layer


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o Keratinization is replacement of cell contents with the protein

keratin; occurs as cells move to the skin surface over 2-4 weeks

KERATINIZATION

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https://www.studyblue.com/notes/note/n/integument-/deck/4421919


Read Disorders: Homeostatic Imbalances (Tortora, p 287) and

define following terms: rheumatism, osteoarthritis, rheumatoid

arthritis, gouty arthritis, lyme disease, aging and strain/sprain.

Then discuss:

- How is psoriasis developed – explain the normal skin biology

and then apply it to psoriasis development

- Think about the causes and possible treatments for psoriasis

within your particular interest.

Non assessable


o Skin Grafts:

• New skin can not regenerate if the stratum basale and its

stem cells are destroyed

• Autograft: covering of wound with piece of healthy skin

from self

• Isograft: from your identical twin

• Autologous skin: transplantation of patient’s skin after it

has grown in culture

Clinical application:


DERMIS

o Structure: connective tissue

layer composed of collagen and

elastic fibers, fibroblasts,

macrophages and adipocytes

o Contains hair follicles, glands,

nerves and blood vessels

o Two major regions of dermis

1. Papillary region

2. Reticular region


1. PAPILLARY REGION

o Top 20% of dermis; finger-like projections

are called dermal papillae

o Structure: areolar connective tissue

containing fine elastic fibers, Meissner’s

corpuscles, free nerve endings, adipose

cells, hair follicles, sebaceous glands,

sudoriferous glands

o Functions: anchors dermis to epidermis;

provides strength, extensibility (ability to

stretch), and elasticity (ability to return to

original shape after stretching)

What is the function of

the Meissner’s

corpuscules and free

nerve endings?


2. RETICULAR REGION

o Bottom 80% of dermis

o Structure: dense irregular

connective tissue that contains

interlacing collagen and elastic

fibers; oil glands, sweat gland

ducts, adipose and hair follicles

o Function: provides strength,

extensibility and elasticity to skin


SKIN COLOUR PIGMENTS

o Melanin: complex polymer derived from

tyrosine; produced by melanocytes in

epidermis

• UV in sunlight increases melanin

production

o Carotene: yellow-orange pigment

(precursor of vitamin A); found in

stratum corneum and dermis

o Haemoglobin: red, oxygen-carrying

pigment in blood cells

• if other pigments are not present,

epidermis is translucent so pinkness will

be evident


The colour of skin and mucous

membranes can provide clues for

diagnosing certain problems, such as

• Jaundice

– Yellowish colour to skin and the whites

of eyes

– Buildup of yellow bilirubin in blood from

liver disease

• Cyanosis

– Bluish colour to nail beds and skin

– Haemoglobin depleted of oxygen looks

purple-blue

• Erythema

– Redness of skin due to enlargement of

capillaries in the dermis

– During inflammation, infection, allergy

or burns

Clinical application


Common disorders linked to melanocytes and melanin biology

are freckles (liver spots), albinism and vitiligo. In groups of 3-4,

pick one disorder and consider:

- Cause of the disorder

- Explain skin biology and how is it impacted by the disorder

- Consider any appropriate treatment within your own

interests



o Thin skin

• Covers all parts of the body except for the palms and palmar surfaces of

the digits and toes

• Lacks epidermal ridges

• Has a sparser distribution of sensory receptors than thick skin

o Thick skin (0.6 to 4.5 mm)

• Covers the palms, palmar surfaces of the digits, and soles

• Features stratum lucidum and thick epidermal ridges

• Lacks hair follicles, arrector pili muscles, and sebaceous glands, and has

more sweat glands than thin skin

TYPES OF SKIN



Structure of skin




Lecture 12:

Functions of skin


Wound healing




Burns




ACCESSORY STRUCTURES

OF SKIN

o Develop from the embryonic

epidermis

o Cells sink inward during

development to form:

• Hair

• Oil glands

• Sweat glands

• Nails


HAIR (PILI)o Present everywhere except palms,

palmar surfaces of the digits, soles

and plantar surfaces of the digits.

o Structure:

• Shaft: above the skin surface

• Root: penetrates the dermis and

subcutaneous layer

• Cuticle

• Follicle

o New hairs develop from cell

division of the matrix in the bulb

o Function: prevents heat loss;

decreases sunburn; eye protection

(eyelashes); senses light touch

(hair root plexus)


HAIR GROWTH

o The hair growth cycle consists of 2 stages:

1. Growth stage

• lasts for 2 to 6 years; matrix cells at base of hair root producing length

2. Resting stage

• lasts for 3 months; matrix cells inactive and follicle atrophies

o Old hair falls out as growth stage begins again (normal hair

loss is 70 to 100 hairs per day)

o Rate of growth and replacement cycle can be altered by

illness, diet, high fever, surgery, blood loss, severe emotional

stress, and gender; hormones influence the growth and loss

of hair; chemotherapeutic agents affect the rapidly dividing

matrix hair cells resulting in hair loss.


TYPES OF HAIR

1. Lanugo

• fine, non-pigmented hair; covers the foetus

2. Vellus hair

• short, fine hair that replaces lanugo; invisible to naked eye

3. Terminal hair

• course pigmented hair; appears in response to androgens

and hair of the head; first eyelashes and eyebrows, then

other body regions


HAIR COLOUR

o Hair colour is due primarily to the amount and type of melanin

o Graying of hair occurs because of a progressive decline in

tyrosinase → decline in melanin production

• Dark hair contains true melanin

• Blond and red hair contain melanin with iron and sulphur added

• White hair has air bubbles in the medullary shaft


GLANDS OF THE SKIN

o Specialized exocrine glands found in dermis

1. Sebaceous (oil) glands

2. Sudoriferous (sweat) glands

3. Ceruminous (wax) glands

4. Mammary (milk) glands


SEBACEOUS (OIL) GLANDS

o Sebaceous (oil) glands are usually

connected to hair follicles; they are

absent in the palms and soles; secretory

portion of gland is located in the dermis

o Produce sebum

• Contains cholesterol, proteins, fats

and salts

• Moistens hairs

• Waterproofs and softens the skin

• Inhibits growth of bacteria and fungi

(ringworm)

o Clinical application: Acne

• Bacterial inflammation of glands

• Secretions are stimulated by

hormones at puberty

gazettereview.com

http://gazettereview.com/2015/07/everything-you-need-to-know-about-acne-and-how-to-cure-it/


SUDORIFEROUS (SWEAT) GLANDS

1. Eccrine sweat glands: extensive

distribution to most areas of skin;

secretory portion is in dermis with duct to

surface → terminate at pores at the

surface of the epidermis

• Regulate body temperature through

evaporation (perspiration)

• Help eliminate wastes such as urea

• Secretions are more viscous

2. Apocrine sweat glands: limited in

distribution to the skin of the axilla, pubis,

and areolae; secretory portion in dermis;

ducts open into hair follicles

health.howstuffworks.com

http://health.howstuffworks.com/wellness/hygiene-tips/body-odor1.htm


CERUMINOUS GLANDS

o Modified sudoriferous glands that

produce a waxy substance called

cerumen

• Found in the outer ear

• Barrier for entrance of foreign

bodies

o Abnormal amount of cerumen in the

outer ear canal can result in blockage

and prevent sound waves from

reaching the ear drum.


STRUCTURE OF NAILS

o Tightly packed keratinized cells

o Nail body:

• Visible portion pink due to

underlying capillaries

• Free edge appears white

o Nail root:

• Buried under skin layers

• Lunula is white due to thickened

stratum basale

o Eponychium (cuticle):

• Stratum corneum layer


NAIL GROWTH

o Nail matrix is below nail root - produces growth

o Cells transformed into tightly packed keratinized cells

• 1 mm per week

o Certain nail conditions may indicate disease



Structure of skin




Lecture 12:

Functions of skin


Wound healing




Burns




FUNCTIONS OF SKIN

o Thermoregulation

o Blood reservoir

o Protection



o Excretion


THERMOREGULATION

o Too cold: shivering and constriction of surface vessels

• Hair mucles puul hairs on end so erect hairs can trap air

• Blood flow to capillaries decreases

o Too hot: perspiration and evaporation

• Hair muscles relax and lie flat→heat escapes; sweat secreted by

sweat glands

• Blood flow to capillaries increases


Thermoregulation when exercising

o In moderate exercise, more blood brought to surface helps

lower temperature

o With extreme exercise, blood is diverted into muscles and body

temperature rises


Intrinsic and extrinsic factors

influencing thermoregulation

Hanna and Teit, 2015


OTHER FUNCTIONS OF SKINo Blood reservoir

• extensive network of blood vessels

o Protection - physical, chemical and biological barriers

• tight cell junctions prevent bacterial invasion

• lipids released decrease evaporation

• pigment protects somewhat against UV light

• Langerhans cells alert immune system


• Touch, pressure, vibration, tickle, heat, cold, and pain arise

in the skin


OTHER FUNCTIONS OF SKIN


• Necessary vitamin for absorption of calcium from food in

the gastrointestinal tract

• activation of a precursor molecule in the skin by UV

light→blood→enzymes in the liver and kidneys modify the

activated molecule to produce calcitriol (the most active

form of vitamin D)

o Excretion

• 400 mL of water/day, small amounts salt, CO2, ammonia

and urea


TRANSDERMAL DRUG

ADMINISTRATIONo Method of drug passage across the epidermis and into the

blood vessels of the dermis

• Drug absorption is most rapid in areas where skin is thin

(e.g. scrotum, face and scalp)

o Examples:

• Nitroglycerin (prevention of chest pain from coronary artery

disease)

• Scopolamine ( motion sickness)

• Estradiol (estrogen replacement therapy)

• Nicotine (stop smoking alternative)



EPIDERMAL WOUND HEALING

o Abrasion or minor burn

o Basal cells migrate across the wound → contact with other

cells stops migration → EGF stimulates basal cells to divide

and replace the ones that have moved into the wound → full

thickness of epidermis results from further cell division


DEEP WOUND HEALING

o When an injury extends to tissues deep to the epidermis, the

repair process is more complex than epidermal healing and

scar formation results.

o Healing occurs in 4 phases:

1. Inflammatory phase

2. Migratory phase

3. Proliferative phase

4. Maturation phase


DEEP WOUND HEALING1. Inflammatory phase

• blood clot unites the wound edges,

epithelial cells migrate across the wound

• vasodilatation and increased

permeability of blood vessels deliver

phagocytes and WBCs

2. Migratory phase• regrowth of epithelial cells and the

formation of scar tissue by the fibroblasts

• tissue filling the wound is called

granulation tissue


DEEP WOUND HEALING

3. Proliferative phase• events of the migratory phase

intensify

4. Maturation phase• the scab sloughs off, the epidermis is

restored to normal thickness,

collagen fibers become more

organized, fibroblasts begin to

disappear, and blood vessels are

restored to normal


EXAMPLE OF PHASES OF

DEEP WOUND HEALING


Fibrosis

o Scar tissue formation (fibrosis)

can occur in deep wound

healing.

• Keloid scar extends into

previously normal tissue

– Collagen fibers are very

dense and fewer blood

vessels are present so the

tissue is lighter in colour

• Hypertrophic scar remains

within the boundaries of the

original wound


BURNS

o Definition: tissue damage from excessive heat, electricity,

radioactivity, or corrosive chemicals.

o Effects:

• Denaturing of proteins in the exposed cells

• Shock due to water, plasma and plasma protein loss

• Circulatory kidney problems from loss of plasma

• Bacterial infection

o Types of burns:

1. First-degree

2. Second-degree burn

3. Third-degree or full-thickness


Types of burns

Third-degree

- full-thickness

- Epidermis, dermis

and epidermal

derivatives

- Damaged area is

numb due to loss of

sensory nerves

First-degree

- Epidermis only

- e.g. sunburn

Second-degree burn

- Epidermis and part of

dermis

- Fluid-filled blisters

separate epidermis and

dermis

- Heals without grafting in

3 to 4 weeks; may scar


BURNS

o Determination of how serious is a burn is done by

considering:

• depth, extent, and area involved

• person’s age and general health

o E.g. when the burn area exceeds 70%, over half of the

victims die

o Two methods for measuring burn extent:

1. rule of nines

2. Lund-Bowder method



RevisionRead one of the following: section 5.7 or Homeostatic

Imbalances (Tortora, p 162 and 164) and define following terms:

photosensitivity, skin cancer, pressure sores and aging. Then in

groups of 2-3 think about:

- What are the risk factors for these conditions and disorders?

- Describe structural and comment on molecular level changes

that occur in these skin disorders and conditions.

- Link the described causes and affected skin physiology to

comment on possible treatments of these disorders within your

particular interest.

Non assessable


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BIOH111 SN24 Lecture IntegumentarySystem · PDF filemelanocytes secrete it in secretory vesicles ... Accessory skin structures ... evaporation (perspiration)