The Integumentary System – Skin!

Steve Bradley Machin L. Norris

Poudre High SchoolAnatomy and Physiology

INTEGUMENTARY SYSTEM Structure - Epidermal layer, Dermal layer, Subcutaneous layer Functions

A. Regulation of body temperature – sweat, vessels dilate for heat loss/heat retention through vessel constrictionB. Protection – keeps water and other molecules in, keeps water and undesirable substances outC. Sensation – detect pain, pressure, temperature, touchD. Excretion – elimination of some nitrogenous waste, excess salt, water (sweat/perspirationE. Immunity - macrophagesF. Synthesis of Vitamin D – sunlight hits skin cells, cholesterol is converted to precursor molecule that aids in absorption of Ca and P

EPIDERMIS – Stratified squamous epithelium, first layer of skinCell Types:a. KERATINOCYTES – in all five layers, more on

the outside, make keratin, sealing cellsb. MELANOCYTES – Produce melaninc. LANGERHANS CELLS – macrophagesd. MERKEL CELLS – sensory cells

First Layer of the Integumentary System Epidermis Five layers of Strata

from deepest to most superficiala. Stratum Basale –

(Germinativum) – deepest, single layer of cells, only layer to undergo mitosis (millions of new cells daily) receives adequate nourishment, contains few keratinocytes, melanocytes, Merkel cells, as are pushed out become more keratinized, new turnover every 35-45 days

b. Stratum Spinosum -contains keratinocytes, Langerhans cellsarise in the bone marrow and migratereceives nourishmentseveral layers thickdoes not divide

c. Stratum Granulosum –3-5 layers of flattened keratinocytes = water repellentlast living layer, receives nourishmenteverything beyond this layer is dead

d. Stratum Lucidum Few layers of dead keratinocytes Found only in thick- skinned areas (pads of feet, palms of hands, calluses – no haire. Stratum Corneum 20-30 layers thick of dead keratin-filled cells, protects against abrasion and penetration, water proof

Second Layer of the Integumentary System Dermis1. Cells of dermis – fibroblasts,

macrophages, adipocytes.2. Thick – palms, soles/Thin –

scrotum, eyelids3. Dermal Papillae – produce

fingerprints, contain tactile receptors called “Meissner’s Corpusles.” These are nerve endings sensitive to touch.

4. Lower Region of the Dermis

a. Consists of dense, irregular connective tissue containing collagen and elastic fibers, adipose tissue, hair follicles, nerves, oil glands, and the ducts of sweat glands.

b. These fibers give skin it’s strength! Extensibility – ability to stretch (ex. Neck, Elbow “chickenskin!”) Elasticity – the ability to return to it’s original shape after

extension or contraction (ex. Pregnancy, Tissue swelling)c. Lamellated Corpuscles – a subcutaneous layer that is sensitive

to pressure

Dermis cont.

Skin Color and Pigmentation

1. Melanin – pigment in the epidermis2. Carotene – pigment in the dermis3. Hemoglobin – pigment in the RBC’s ( passes thru

capillaries in the dermis)

A. Pigments

Albinisim – the inability to produce melanocytes

1. Inherited through parents via an altered copy of genes that does not allow the body to make the usual amount of a pigment called melanin.

2. Melanin is a dark compound that is called a photoprotective pigment.

3. Major role of melanin is to absorb the UV light that comes from the sun so that the skin is not damaged.

* (see diagram 6 and 7 for inheritance)

Albinism (cont.)4. Common eye problems resulting from albinism

a. Nystagmus – an involuntary movement of the eyes back and forth (stand up and spin, then watch eyes. diagram 1)b. Photophobia - sensitivity to light but, it does not

limit albinos from going out into the sunlight!c. Strabismus – the eyes do not fixate and

track together, but they do have some depth perceptiond. Iris color – usually blue/gray or light brown. The reddish reflection comes from the retinaon the inside of the eye.

(diagram 1).e. Unusual patterns of sending nerve signals

from the eye to the brain (diagram 3)

Malignant Melanoma1. Melano = dark colored;

oma = tumor2. Cancer of the Melanocytes3. Due to the repeated exposure

of ultraviolet radiation – amount of darkness of melanin increases. Tanning Beds (=) Stupid Idea!!!

Accessory Organs of the Skin –develop from the embryo of the developing fetus.

Hair – Protect the body

Glands – help regulate the body

Nails – protect the body

Hair

1. Primary function is protection, guards the scalp from injury and the suns rays.

a. Eyebrows and Eyelashes – protect the eyes from foreign particles.

b. Nostril hair – protects against inhaling insects and foreign particles.

Hair - Composition Hair is Keratinized cells, that consist of a shaft and a

root.a. SHAFT – projects above the surface of the skin.b. ROOT – below the surface that penetrates into the

dermis and into the subcutaneous layer.c. HAIR FOLLICLE – composed of two layers of epidermal

cells :External and Internal root sheaths surrounded by a connective tissue sheath.

Anatomy of the Hair Follicle:

More Hair Composition!!!

d. BULB – onion shaped structure, contains papilla of the hair, which have many blood vessels and provide nourishment for the hair.

e. MATRIX – included in the bulb, produces new hairs by cell division when older hairs are shed.

Growth cycles of the hair.a. GROWTH STAGE – Cells of matrix differentiate Keratinization Death*New cells are added at base of root making the hair grow longer.

b. RESTING STAGE –Growth of the hair stops, innactive matrix and shortening of hair

follicle.

c. NEW GROWTH CYCLE – *New hair replaces old hair and old hair is pushed out of the growth

cycle.

Thought you were done…..Nope!Melanin –hair color is due to melanin (brown,

black, blonde). **FYI – decreased melanin production and increased air in the hair shaft produces grey and white hairs.

“Canadian” Goosebumps! – due to the contraction of the arrector pili, under stresses of froght and cold which pull hairs into a verticle position.

Glands1. Sebaceous Oil Glands – secreting portion lies in the

dermis and open into the necks of hair follicles or directly onto a skin surface.

*no sebaceous glands on the palms or solesa. Sebum – oily secretion that ….

- Keeps hair from drying out- Prevents excessive evaporation of water from skin- Keeps skin soft- Inhibits the growth of certain bacteria

Glands Again!

BLACKHEADS – accumulated sebum and enlargement of sebaceous glands in face.PIMPLES – sebum acts as a nutrient to bacteria – that’s why you get the yucky puss out of them!

Glands – almost…….2. Sudoriferous (Sweat) Glands – Two types

a. APOCRINE SWEAT GLANDSa. armpit, pubic region, and areolae of breasts.b. produce sticky viscous secretion

b. ECCRINE SWEAT GLANDS – more watery secretion during emotional stress or “cold sweat.”

a. not found in lips, nail beds, labia minora, glans penis, and eardrums.

b. Palms and soles!!

Bad Odor (BO)Perspiration or Sweat (comes from the eccrine)

– functions to….- Help regulate body temperature- Elimination of wastes

*Antiperspirants v.s. Deodorants

“The Last of the Sweat Glands”

3. Ceruminous Glands – located in the outer ear canal.

a. EAR WAX = cerumen (cera = wax)*a combination of ceruminous secretions and sebaceous glands

b. HAIRS + EAR WAX = provide a sticky barrier against foreign bodies.

Nails

1. Structure - Plates of tightly packed, keratinized cells of the epidermis.

a. NAIL BODY – visible portion of nail (PINK PART)b. FREE EDGE – part that extends past the end of the

finger or toe.c. NAIL ROOT – non-visible portiond. LUNULA – thickened, whitish semilunar areaNear the nail root and cuticle

2. Growth of the nailsa. Occurs by transformation of superficial cells of the nail

matrix into nail cells. b. Growth slower in toenail.c. The longer the digit the faster the nail growsd. The more the had used, the faster the hand nail growth.e. Nails help us grasp and manipulate objects and provide

a protection against damage to the fingertips.