Chapter 5: Integumentary System

Skin: The Largest Organ. Tough outer protective covering Functions: 1. Protection 2. Defense 3. Prevention of Dehydration 4. Body Temperature 5. Excretion of Waste 6. Reception of Stimuli 7. Vitamin D Synthesis 8. Communication

1. Protection - of underlying tissues and organs from fluid loss, abrasion and impact and chemical attack and microbial infection.

2. Defense- against microbes3. Excretion- of salts, water and organic

wastes and by integumentary glands.4. Thermoregulation of body temperature…via

evaporation or insulation( Keratin)5. Synthesis of Vitamin D3, a steroid, a

hormone necessary for normal calcium absorption.

6. Detection of touch, pressure, pain…general senses that are relayed to the central nervous system.

Functions of SKIN or Subcutaneous Membrane

What is it? The skin and its derivatives (sweat and

oil glands, hair and nails) serve a number of functions, mostly protective.

Integumentary System

Skin Structure

Figure 4.4

Or cornification, is the formation of protective , superficial layers of cells filled w/ keratin.

Keratinization

Epidermis – outer layer◦ Stratified squamous

epithelium◦ Often keratinized

(hardened by keratin) Dermis Aeeolar and Dense

Irregular Connective saaaive tissue

Skin Structure

Figure 4.3

1. Epidermis- Contains either 4 or 5 layers depending on if THIN or THICK skin.

THIN: covers most of body ( 4 layers)(.08mm)

THICK: soles of feet, palms of hands (.5mm) (5 layers here.

Stratum: 1. germantivum (basale) 2. spinosum, 3.granulosum, 4. Lucidum (only in thick skin), and 5.corneum.

Example: Stratum germativum (basale)for 1st layer

SKIN: 2 TISSUES

Thickness = 0.6mm to 3mm Composition

◦ collagen, elastic and reticular fibers, fibroblasts Dermal papillae - extensions of the dermis into

the epidermis◦ forming the ridges of the fingerprints

Layers◦ papillary layer◦ reticular layer is deeper part of dermis

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Dermis

The Dermis

2 COMPONENTS: 1) Papillary Layer- Consists of Areolar Tissue.

Contains capillaries, lymphatics, and sensory neurons that supply the surface of the skin. Projections: Dermal Papillae.

2) Reticular Layer- deep to the PL, Contains blood vessels, deep pressure receptors

called* Pacinian corpuscles and Macrophages. Also tissue : consists of interwoven layer of dense

irregular connective tissue; containing collagen and elastin fibers. Appendage structures extend into dermis.

Dermis:Components & Characteristics

Subcutaneous Layer Located under the dermis Mostly adipose Functions

◦energy reservoir◦thermal insulation

Hypodermic injections ◦highly vascular

Layers of Epidermis

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Cell and Layers of the Epidermis

Layers of Epidermis

Stratum basale (germinativum) Stratum spinosum (prickly layer) Stratum granulosum (granular) Stratum lucidum (clear layer) Stratum corneum (horny layer)

Epidermal Cell Types

1. Stem Cells (Basale)- Gives rise to keratinocytes

2. Keratinocytes (Basale)

Synthesize keratin (insoluble protein) provides strength and waterproofing

3. Melanocytes (Basale)

pigment cell: produce melanin

4. . Langerhans Cell - (Spinosum and Grandulosum) macrophages produced in bone

marrow migrate to epidermis participate in immune responses

5. . Merkel Cells (Basale)

Associated with touch sensors

Single layer cells on basement membrane Cell types in this layer stem Cells –become keratinocytes

◦ keratinocytes to replace epidermis

◦ melanocytes distribute melanin through cell processes melanin picked up by keratinocytes

◦ merkel cells are touch receptors form Merkel disc

Stratum Basale

Skin color…….. 1. Oxyhemoglobin

Underlying blood vessel gives skin a reddish color 2. Carotene: (pigment)

From fruits and vegetables (and egg yolk) Converted to Vitamin A in skin Gives skin a yellowish color

3. Melanin: (pigment)

Protein pigment from melanocytes Synthesized from tyrosine amino acid Contributes brown to black, depending on how

much

Pigment (melanin) produced by melanocytes

Color is yellow to brown to black

Melanocytes are mostly in the stratum basale

Amount of melanin produced depends upon genetics and exposure to sunlight

Melanin

Melanocytes deeper in the epidermis are stimulated to produce new melanin granules. These new granules are transferred to keratinocytes in the upper cell layers of the skin. These granules become positioned in the outer portions of the cells above the cell nuclei, thus providing additional protection.

 

Melanocyte Stimulation

These are found mostly in the stratum basale

Everyone has the same number of melanocytes.

The darker skin a person has depends on how much melanin a particular melanocyte produces and the size of the granules. This is determined by one’s genetics.

UV rays can stimulate additional melanin production.

Melanocytes

Here’s How it Works

Melanocytes deeper in the epidermis are stimulated to produce new melanin granules. These new granules are transferred to keratinocytes in the upper cell layers of the skin. These granules become positioned in the outer portions of the cells above the cell nuclei, thus providing additional protection.

 

Melanocyte Stimulation

If Melanocytes on Bottom, How Does Skin Get Tan on Top?

Melanocytes have extensions that transfer the granules to surface cells by a process known as Cyocrine Secretion.

Sebaceous Gland Types…… 1. Associated with hair follicles Release secretions via ducts through hair follicles Cover the body: Except:

Dorsal surface of feet Palms of hands Soles of feet

Most abundant: Face and scalp 2. Not associated with hair follicles Mostly inactive in childhood

Lips Labia minora Ducts open directly to skin surface Tip of penis

Contain special white blood cells from the lymphatic system. Help protect body from pathogens.

Stratum Spinosum

Statum Grandulosum Produces lipid-filled vesicles that

release a glycolipid by exocytosisto waterproof the skin

Statum Lucidum Thin translucent zone seen only in

thick skin ( palms and soles of feet)

Cells have no nucleus or organelles

Stratum Corneum The most superficial layer of epidermis 20- 30 layers thick Cornified, ABSOLUTELY dead ABSOLUTELY flattened These take up 75% of the epidermis. They exfoliate continuously.

Basal – arise from the layer stratum basale. Least malignant, most common. Cannot form keratin ( soft). Looks like a mound. No boundary between epidemis and dermis.

Squamous – arise from statum spinosum. Characterized by pearly beaded edge. These will metastasize into the lymph nodules if left untreated and can be lethal.

Melanoma- rarest but most deadly. Develops from pigmented moles. 5% survival rate.

Skin Cancer: 3 Types

ABCD Test For Melanoma

A – Asymmetrical; the two sides of the pigmented spot do not match.

B- BORDERS-irregular boarders; not smooth with indentations apparent

C- COLOR- pigment contains areas of different colors

D- DIAMETER- larger than ¼ inch

Skin Cancer: RFs over exposure to UV light. Frequent irritation to skin by infections,

chemicals or physical trauma living at high altitudes, fair skinned people, having a lot of moles family history of the disease one or more severe sunburns as a child

Specialized Stuctures ( appendages…found in DERMIS) During Embryogenesis, parts of stratum basale push down into dermis. They multiply and differentiate into: 1. hair 2. glands 3. nails r 3. nails

Afferent Neuron – Moving away from a central organ or point Relays messages from receptors to the CNS

                                                                                       

SO …What are SENSORY RECEPTORS?

Do these belong to the PERIPHERAL NERVOUS SYSTEM or Integumentary System???

More Than One Kind….

Named after discovered

Theses are sensory receptors that detect

Pacinian Receptors

Pacinian Receptor

dermal Glands……. 2. Sweat Glands: (Sudoriferous glands)

They are Merocrine glands Sweat: water

salts urea uric acid (trace)

Function Help regulate body temperature Communicate emotional states Excrete excess water and small amounts of nitrogen

sss

Sebaceous glands

associated with hair follicle

Eccrine glands , that is SUDORIFEROUS or SWEAT GLAND empties onto Skin

Sebaceous (Oil) GlandsSecrete oil or sebum

Usually secretes into hair follicleLubricates hair and skin• softens dead cells--pliability• slows water loss

Everywhere except palms, soles

• bactericidalStimulated by hormones (androgens)

Apocrine Vs. Eccrine Glands

Sweat Gland Types ………….. 2. Apocrine Sweat Glands:

Analogous to sexual sweat glands of other animals Found in association with hairs, armpits, genital areas Discharges thick sticky odorless secretion into follicle.

Bacterial decomposition causes a distinctive body odor

Function is to produce an odorous sweat DISPITE its NAME…IT IS A MERICRINE

GLAND…EXOCYTOSIS !!

What Did You Say??? Ceruminous glands- This are modified

(eccrine) sweat glands in the passageway of the external ear. Their secretions combine w/ sebaceous glands forming CERUMEN….or earwax. Together w/ tiny hairs traps foreign particles.

Hair: 1. Function:

Protects the head from injury Protects the head from sun Eyelashes protect eye from foreign matter Eyebrows protect eye from perspiration Pubic hair expresses sexuality

Hair Growth Cycles: Not synchronized in humans so some follicles are always growing while others are resting

a. Growing phase Scalp hair grows about 4-6 inches per year Cutting or shaving it has no effect on its

growth b. Resting phase

No growth

HAIR STRUCTURE ( flexible epithelial structure)

contains a MATRIX- the growth zone ..a zone of stratum basale, hair bulb at inferior end of follicle. (ACTIVELY DIVIDING Epithelial Cells—alive)

Root- Part of hair enclosed in follicle—now keratinized and dead

Shaft- Hair part that projects from surface of the scalp or skin.

Hair and Hair Follicles

HAIR FOLLICLE

The part of the hair covered by the follicle is called the ROOT.

Hair exposed is called the SHAFT.

Hair is formed from STRATUM BASALE Cells in GROWTH ZONE of MATRIX of HAIR BULB. This is nurished by DERMAL Papilla .

Figure 6.7

Figure 6.10c

HAIR YOU SEE IS DEAD SOFT KERATIN in the Medulla

HARD KERATIN in the Cortex and Cuticle Hardest and Outermost is the CUTICLE

Associated Hair Structures

Hair follicle◦ Dermal and epidermal

sheath surround hair root Arrector pilli ( when

erect pull hair straight and causes “goose bumps”)◦ Smooth muscle

Sebaceous gland Sweat gland

Figure 4.7a

Hot water, sunlight, radiation, electric shock or acids and bases

Death from fluid loss and infection Degrees of burns

◦ 1st-degree = only the epidermis (red, painful and edema)

◦ 2nd-degree = epidermis and part of dermis (blistered) epidermis regenerates from hair follicles and sweat glands

◦ 3rd-degree = epidermis, dermis and more is destroyed often requires grafts or fibrosis and disfigurement may

occur Treatment – IV nutrition and fluid

replacement, debridement and infection control

Burns

Figure 6.12bb

Figure 6.12ca

Figure 6.12cb

Table 6.2