Biology 322Human Anatomy I

Integument

Functions of Integumentary System (skin & its products)

Barrier to keep water and solutes in

Barrier to keep bacterial, dirt, etc. out

Protection against abrasion

Contains sensory receptors for touch, temperature, pressure, pain, etc.

Temperature regulation via hair, sweat, & amount of blood flow

Blood reservoir

Synthesis of vitamin D

Excretion

Three Layers of skin:

Epidermis: Avascular. Depends on blood vessels in underlying dermis for its nutrition

= Single row of dividing cells

(Epidermis)

= Three or four layers of cells; Some cell division

= Three or four layers of cells; Actively synthesizing protein keratin

= One or two layers of dying cells Not present in thin skin

= Many layers of flat, dead, scale-like cells full of keratin

(Connective tissue)

Primary cell type in epidermis = which produce large amounts of protein

Other cell types:

Two related forms of melanin:

Black or brown Responsible for dark skin or hair

Red or pink Responsible for pink skin (lips, nipples, glans of clitoris or penis, freckles) and red hair

Both synthesized

Keratinocytes move from stratum basale to stratum corneum, dying as they do so. Average = 5 - 6 wks

- Keratinocytes in stratum basale (& stratum spinosum) lie along basement membrane; divide by mitosis

- Older cells die but remain attached to each other

- Older ones pushed toward surface by newer cells

- Cells eventually shed from stratum corneum

- Keratinocytes synthesize large amounts of keratin and flatten out as they move toward surface

- Melanocytes transfer melanin to keratinocytes

(Epidermis)

Dermis:

Two Layers:

Dermis = Dense irregular connective tissue. Thus:

Cells =

Fibers =

Dermis:

Contains many types of sensory receptors for touch, pressure, vibration, pain, temperature, etc.

Some = simple nerve endings

Others = complex structures with multiple cell types

Appendages of the skin

All begin as epidermis of embryo; grow down into dermis

Hair

- Distribuled over all skin except: palms of hands soles of feet nipples glans of penis & clitoris minor labia

- Formed in follicles located deep in dermis

- Consists of layers of dead, highly keratinized keratinocytes

Black or brown

Blond

Red

Gray or White

Each hair is associated with:

Sweat Glands

Two specially modified sweat glands:

Sebaceous (oil) glands:

- Branched tubular glands

- Duct opens into opening of hair follicle

- Secretes sebum, consisting of lipids, proteins, ions, carbohydrates,

Nails:

- Tips of fingers and toes - Thick layer of densely packed keratinocytes - Produced by

Deeper layers of epidermis =

Average growth:0.5 mm per week

Carcinomas (cancers) of the skin:

Basal Cell Carcinoma: Keratinocytes of stratum basale proliferate, invade dermis Relatively low malignancy

Squamous Cell Carcinoma: Keratinocytes of epidermis proliferate. May invade dermis Moderate malignancy

Malignant Melanoma: Melanocytes of epidermis proliferate, invade dermis Highly malignant