The Integumentary System

General Info…….. Skin has 2 layers Epidermis - outer layer Dermis – inner layer Sweat glands excrete sweat through pores. Sweat is made up of urea, salts, and water. Body’s first line of defense! Largest organ of the body.

The “Birthday Suit” Combination of 4 main tissues: Epithelial – outer layer Connective – underlies dermis Smooth Muscle – goose bumps Nervous – sensory receptors

Functions of the Skin Protection Temperature regulation Sensations Storage of chemical compounds Excretion of wastes Synthesis of compounds Determines characteristics

The Skin FG04_02.JPG Title: Components of the Integumentary System Notes: Relationships among the major components of the integumentary system (with the exception of nails, shown in Figure 4-15). Keywords: integumentary system, cutaneous, epidermis, dermis, papillary layer, reticular layer, hair follicles, exocrine glands, nails

Epidermis Outer layer of dead skin cells called cuticle . Layer you see everyday. “Ashiness” is caused by this layer of dead skin cells being very rough and raggedy. DUST you see around is made up of dead skin cells! Under the cuticle is another layer of living epithelial cells that make up the rest of the epidermis.

Epidermis and Dermis Epidermis is avascular (no blood vessels) Dermis is highly vascular (has blood vessels) Epidermis receives nourishment from dermis Cells far away from nourishment die

Epidermis FG04_03.JPG Title: The Structure of the Epidermis Notes: A light micrograph through a portion of the epidermis, shows the major stratified layers of epidermal cells. Keywords: epidermis, structure, layers, stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum germinativum, dermis

Dermis Thick layer under the epidermis Contains blood vessels Oil glands Sweat glands Hair follicles Fat tissue Nerves Connective tissue

Deeper Layer of the Dermis Dense connective tissue Contains Blood vessels Glands Deep pressure receptors Attached to underlying organs by the subcutaneous layer Loose connective tissue Packed with adipose cells Stabilizes position of skin

Human Anatomy, 3rd edition Fingerprints Human Anatomy, 3rd edition Prentice Hall, © 2001

What Else Comes from the Epidermis? Hair Glands Nails

Functions of Hair Protection Thermoregulation Sensory Minor role in humans

Hair Structure Shaft Superficial portion Root Below the surface Cuticle Outermost layer of hair Hair develops in follicles Downward continuation of epidermis

Hair Structure FG04_10A.JPG Title: Hair Follicles Notes: Hairs originate in complex organs termed follicles. (a) A longitudinal section and a cross section through a hair follicle. (b) and (c) A section along the longitudinal axis of a hair follicle. Keywords: hair follicle, longitudinal section, cross section, sebaceous gland, arrectory pili muscle, cortex, cuticle, internal root sheath, connective tissue layer, glassy membrane, external root shaft

Growth of Hair At the base of the follicle, hair papilla Bulb Contains blood vessels and nerves Nourishes hair Bulb Contains matrix – epithelial cells responsible for growth Contains melanocytes

Smooth muscle attaches to follicle Raises hairs Arrector Pili Smooth muscle attaches to follicle Raises hairs Response to fright or cold Function?

Glands Sebaceous glands Connected to hair follicles Secrete a waxy, oily substance (sebum) Blackheads Secretion increases at puberty

Sebaceous Glands FG04_13A.JPG Title: Sebaceous Glands and Follicles Notes: The structure of sebaceous glands and sebaceous follicles in the skin. Keywords: sebaceous glands, sebaceous follicles, structure, sebum, germinative cells

Glands Sweat glands Found just about everywhere Produce “perspiration” Water, salt, met. Wastes Function – cooling of the body Scent Glands Specific type of sweat gland Found near hair follicles Axillary & genital regions Develop at puberty

The Skin with Sweat Glands FG04_02.JPG Title: Components of the Integumentary System Notes: Relationships among the major components of the integumentary system (with the exception of nails, shown in Figure 4-15). Keywords: integumentary system, cutaneous, epidermis, dermis, papillary layer, reticular layer, hair follicles, exocrine glands, nails

Nail Structure Nail body Free edge Nail root Matrix Lunula (moon)

Nail Structure FG04_15.JPG Title: Structure of a Nail Notes: These drawings illustrate the prominent features of a typical fingernail as view from the surface and in section. Keywords: fingernail, hyponychium, nail bed, lateral nail groove, lunula, eponychium, phalanx, dermis, epidermis

The skin also helps control body temperature- Homeostasis! When you sweat, heat leaves the body through your pores. When the sweat hits the outer surface of the skin, it is cooled by the air. This lowers your body temperature.

The Amazing Body- Skin

Use the following vocabulary to label the diagram: hair shaft, oil (sebaceous)gland, fat cells, erector pili muscle, blood vessels, nerve endings, epidermis, dermis, cuticle, epithelial cells, hair follicle, sweat gland, connective tissue