The Integumentary System

Components Skin Nails Hair follicles Sebaceous glands(oil) Sweat (sudoriferous) glands

Functions of the Skin Protection (1st line of defense) Regulates body temp. Conserves water inside body Contains sensory receptors Makes biochemicals Excretion of wastes *Skin is the largest organ of the body

Layers of Skin Skin has 3 layers 1. Epidermis - outer layer 2. Dermis – middle layer 3.subcutaneous/hypoderm- bottom/deepest layer

1. Epidermis Outer layer of skin cells Avascular- lacks blood vessels, fed by diffusion Acts as a mechanical barrier Made of many layers of cells Top cells dead Bottom layer alive- multiply and new cells are pushed upward (EX-”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! )

Epidermis Keratinization- process where keratin develops in a cell, which hardens it, and makes the cell layer waterproof Contains melanocytes- cells which contain the pigment melanin Difference is skin color is due to % of melanin in the cell .( We all have the same # of cells, just produce a different amt. of melanin.) Amt. of melanin increases with UV light exposure Too much exposure=melanoma (skin cancer)

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

Layers of Epidermis 5 layers “Cows Love Grass So Badly” Stratum corneum (corny/scaly) Stratum lucidum (palms of hands, feet, absent in thin skin) Stratum granulosum(granular) Stratum spinosum(spiny/prickly) Stratum basale (base/bottom) *1st degree burns

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

2. Dermis Thick layer under the epidermis Collagen, elastic layer Vascular-Contains blood vessels Oil glands (sebaceous) sweat glands Hair follicles Nerves Arrector pili muscle *2nd degree burns

3. Subcutaneous Layer AKA- Hypodermis Contains Fat tissue in adipose cells Thickens w/ weight gain Stabilizes position of skin Insulates(temp. regulation) Larger branches of blood vessels *3rd degree burns

Accessory Organs of the Skin Hair/hair follicles 2. Sebaceous glands 3. Nails 4. Sweat glands

Hair Structure Found in Dermis of skin Cells of hair follicle grow and develop in the blood vessels As cells move upwards they become keratinized and die Melanin – pigment that contributes to dark hair color

Smooth muscle attaches to follicle Raises hairs Arrector Pili Smooth muscle attaches to follicle Raises hairs Response to fright or cold Pulls hairs upright to create a layer of warm air on surface of skin

Functions of Hair Protection Sensory perception Thermoregulation (insulation) -Minor role in humans (exception- Hypertrichosis)

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

Sebaceous Glands Connected to hair follicles Secrete a waxy, oily substance (sebum) Functions of Sebum- -keeps skin soft -keeps skin pliable -keeps skin waterproof 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

Nail Function and Structure Protective covering on fingertip used for picking, scratching, grooming Keratinized, stratifies squamous cells make nails hard Nail root bed – area where new cells are formed

Sweat Glands Sweat glands Found just about everywhere on body Dermis layer of skin Produce sweat aka perspiration Water, salt, wastes (toxins), urea, and uric acid Avg.- @500 mL/day, up to 12 L/day Function – cooling of the body, releasing scent, producing milk, ear wax

Sweat Gland Types Eccrine and Apocrine, two types are different in size and the age they become active Eccrine- most numerous type, found all over the body particularly on the palms, soles of the feet, and forehead, exits pores Apocrine is mostly the armpits. They end in hair follicles instead of or pores. modified- includes scent glands, mammary glands, ceruminous (produce ear wax), ciliary- eyelid

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.

Regulation of Body Temperature Normal body temp- 37 C, 98.6-98.8 F Controlled by hypothalamus of brain Amt. of heat produced is balance by the amt. of heat lost Cellular chemical rxns create heat Muscle contraction creates heat Homeostatic response when exposed to an increase in temp. or a decrease in temp. 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

What happens if body temp. is too high? Body has mechanisms to rid itself of excess heat- Warmed blood reaches hypothalamus nerve impulses respond more blood sent to limbs  flushed skin Vasodilation- blood vessels dilate, skin releases heat, hair lays flat Activation of sweat glands- moisture allows more heat to be released Outcome- Overall temp. decreases 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

What happens if body temp. is too cold? Mechanisms to save heat and create heat in response to cold- Thermoreceptors send signals to hypothalamus Vasoconstriction- blood vessels constrict to reduce heat loss more blood in corepale Deactivation of sweat glands If temp. is still too low, muscles will contract (shivering) to create heat, hair stands up Outcome- Increase in overall body and blood temp. 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

Table 5 - Hypothalamic Regulatory Center Structures When Body Cools When Body Warms Superficial blood vessels Constricts Dilates Sweat glands Inactivates Activates

Veins Constrict (narrow) Veins dilate (widen)

Controlling body temperature Body temperature is controlled by the thermo-regulatory center in the ________. It is kept at 370C as this is the best temperature for __________ to work in. If the body becomes too hot then blood vessels _________ and sweat glands release ________. If the body is too ______ then blood vessels constrict and muscles start to __________. Words – sweat, enzymes, cold, dilate, shiver, brain

Checkpoint What is the normal body temperature? What part of the brain controls temp.? How does the body respond to too much heat? How does the body respond to cold temp.? What type of muscle contracts to cause shivering? What is the difference between vasoconstriction and vasodilation? 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