Four Types of Membranes
1. Serous membranes
- line body cavities that do not open to the outside
- layer of simple squamous epithelium and layer of
loose connective tissue
-secretes serous fluid which lubricates
2. Mucous membranes
-line cavities and tubes that open to the outside of the
body
-epithelium overlying a layer of connective
-secrete mucus
3. Synovial membranes
-form the inner linings of the joint cavities between the
ends of bones (freely moveable joints)
-fibrous connective tissue overlying loose connective
tissue
-cells secrete a thick, colorless synovial fluid into the
joint cavity which lubricates the ends of the bones
4. Cutaneous membrane
- The skin (how many layers?)
The Integumentary System
Skin - 1st line of defense, prevents water loss, waterproofs
the body
Hair - insulates the body, receptor for touch
Nails - protects distal phalanx (fingers /toes)
Sebaceous glands - lubricates the skin, discourages growth
of bacteria
Sweat glands - temperature regulation
The Skin
A. The largest organ of the body and vital in maintaining
homeostasis
B. Two distinct layers, some say three
1. Epidermis
a. most superficial layer
b. half the thickness of a piece of paper
c. varies in thickness
(eyelids
and sole of foot)
d. avascular, it is nourished by the blood vessels in the
dermis
e. keratinization is when the older cells harden, the cytoplasm
of the skin cell fills with the protein keratin
f. specialized cells known as melanocytes produce melanin
1) melanin is a dark pigment in the deeper layers of the
epidermis that absorbs light energy and so protects the
deeper cells from UV light
2) skin color is due to the amount of melanin produced but
color is also influenced by environmental and physiological
factors
2. Dermis
a. binds the epidermis to underlying tissue (basement
membrane)
b. gives skin its strength and elasticity
c. vascular which supply nutrients to all skin cells
d. nerve fibers are scattered throughout as well as sensory
receptors (touch, pressure, heat, pain)
3. Subcutaneous layer
a. aka Hypodermis
b. adipose tissue which insulates (conserves body heat
and keeps out outside heat)
c. vascular that supplies skin and adipose tissue
Hair Follicles
A. Hair is present on all skin surfaces except...
B. hair develops from a group of skin cells at the base of a tube
called a hair follicle
1. follicle extends from the dermis to the surface and
contains the hair root (bulb)
a. a bundle of smooth muscle cells form the
arrector pili muscle that is attached to each follicle
b. the hair stands on end when the muscle
contracts
2. hair shaft extends away from the surface
a. this is dead cells
b. process of keratinization
3. sebaceous glands usually are attached to hair follicles
4. hair color
Nails
A. unguis, onych
B. protective covering at the ends of fingers and toes
C. consist of keratinized stratified squamous cells with very
hard keratin
D. form by cell division in the nail root
1. whitish half-moon-shaped area at the base of the nail
is the lunula and is the growing region
2. skin at base is the eponychium (cuticle)
3. as the nail develops it slides forward over a layer of
epithelium called the nail bed (matrix)
Sebaceous Glands
A. aka oil glands
B. usually attached to hair follicles
C. they are holocrine glands
1. secrete an oily mixture called sebum through small
ducts into the hair follicle
2. Sebum helps keep the hair and skin soft, pliable, and
waterproof, discourages bacteria
Sweat Glands
A. aka sudoriferous glands
B. exocrine glands that are widespread in the skin but are most
numerous in the ____
C. each gland consists of a tiny tube that originates as a ballshaped coil in the deeper dermis or superficial subcutaneous
layer
D. fluid (sweat) is carried away in a duct, which opens at the
surface as a pore
E. sweat is mostly water, but it also contains small quantities of
salt and wastes (urea, uric acid)
Regulation of Body Temperature
Healing of Wounds