Tissue Notes

tissues

tissues

groups of cells that are similar in structure that work together to perform a specific function

histology

the study of tissues

epithelial tissue

Coverings and linings:

• epidermis

• ventral cavity organs

• line internal spaces (lumen of small intestine)

• line body cavities

• line ducts

epithelial functions

1. Protection (epidermis)

2. Absorption (lining of intestine)

3. Secretion (ducts of glands)

4. Excretion (epidermis and kidney capillaries)

5. Filtration (lining of kidney capillaries)

Classification of epithelial tissue

classified by number of cell layers and shape of the cells

simple squamous

single layer of flattened cells

Function:

• allows for easy passage of substances (gas exchange)

Location:

• lining air sacs (alveoli) of the lungs

• lining capillaries

simple cuboidal

single layer of square shaped cells with large centrally located nuclei

Functions:

• secretion

• absorption

Locations:

• lining ducts of glands (goes with secretion)

simple columnar

single layer of elongated cells with a single nucleus located near the basement membrane

Functions:

• protection

• absorption

• secretion

Locations:

• line small intestine, stomach, and large intestine (absorption)

• line uterus

pseudostratified columnar

single layer of elongated cells with scattered nuclei; all cells touch the basement membrane

Functions:

• secretion

• protection

Locations:

• lining trachea (cilia move debris out of trachea)

stratified squamous

many layers of cells; cells nearest the surface are flattened, while the deepest layers are cuboidal or columnar

Function:

• protection

Locations:

• keratinized stratified squamous (epidermis)

• non-keratinized (mouth, vagina, throat, anus)

keratinization

accumulation of the protein keratin, becomes hardened and dies = dry, tough, protective surface

stratified cuboidal

2-3 layers of cuboidal shape that form the lining of the lumen

Function:

• secretion

Location:

• lining ducts of glands

stratified columnar

2-3 layers of elongated cells; basal layer contains cuboidal cells

Location:

• part of male urethra

• vas deferens

stratified transitional

many layers of irregularly shaped cells that change shape in response to tension

Function:

• distensibility-stretches easily to allow urine to fill bladder

Location:

• lining urinary bladder and ureters

connective tissue

most abundant tissue type

made up of different types of cells in varying amounts of a nonliving substance around the cells, called the matrix

cells are farther apart then epithelial cells

functions of connective tissue

1. bind structures together

2. provide support

3. serve as frameworks

4. fill spaces

5. store fat

6. produce blood cells

7. protect against infections

8. help repair tissue damage

adipose tissue

closely packed adipocytes (fat cells)

connective tissue

Location:

• under the skin, around heart, kidneys, eyeballs, breasts

Functions:

• energy storage

• insulation

• protection

tendons

attach muscle to bone

connective tissue

Functions:

• attachment

• tensile strength - resistance to pull

Poor blood supply = slow to no healing

ligaments

attach bone to bone

connective tissue

Functions:

• attachment

• tensile strength - resistance to pull

Poor blood supply = slow to no healing

blood

cells in a fluid matrix called plasma

blood cells are produced in red bone marrow - hematopoiesis

location = within heart and blood vessels

function = transport of gases, nutrients, waste

red blood cells (erythrocytes)

transport gases

white blood cells (leukocytes)

fights against infections

specialized WBCs found in blood and lymph called lymphocytes

platelets (thrombocytes)

help clot blood

muscle tissue

1. contracts, moving structures attached to it

2. muscle cells (myocytes) also called muscle fibers

3. skeletal muscle makes up about 40% of body weight and smooth and cardiac makes up about 10%

4. 3 types

skeletal muscle tissue

1. function - movement of body parts, writing, talking, singing, chewing, walking, etc

2. usually attached to bone

3. voluntary muscle control

4. contains striations - alternating light and dark cross markings

5. each cell is multinucleated

6. contracts when stimulated by a nerve cell, relaxes when it is no longer stimulated

cardiac muscle tissue

1. found only in the heart

2. cells are striated, branched, joined end to end, and interconnected in a complex network

3. each cell has a single nucleus

4. specialized intercellular junction - the connection between these cells - called intercalated discs

5. involuntary control

6. can continue to function without nervous stimulation

7. function is to pump blood

smooth muscle tissue

1. no striations

2. short and spindle shaped cells

3. each cell has one central nucleus

4. involuntary control

5. found in hollow internal organs - stomach, intestines, bladder, uterus, blood vessels

6. moves food through digestive tract, constricts blood vessels, empties bladder

nervous tissue

found in brain, spinal cord, and peripheral nerves

neurons

1. sense certain types of changes

2. have dendrites, which receive sensory information and transmit the message as an electrical signal to the axon. The axon sends the message to the next neuron or to muscles or glands.

3. function is to coordinate, regulate, and integrate many bodily functions

neuroglia

1. supporting cells of the nervous system

2. bind and support nervous tissue

3. carry out phagocytosis - helps protect nervous tissue by engulfing cellular debris, waste, and foreign material

4. connect neurons to blood vessels

5. involved in cell to cell communication