Anatomy and Physiology Unit 2: Tissues

Tissues

Groups of cells that are similar in structure and function

4 types of tissue

epithelial, connective, muscle, nervous

Tissues differ in

-cell size, shape, and arrangement, kind of intercellular substance, and location and function

Estology

study of tissues

epithelial tissue

a sheet of cells that covers a body surface or lines a body cavity

characteristics of epithelial tissue

cellularity, specialized contacts, polarity, support by connective tissue, avascular but innervated, regeneration

Cellularity

Composed almost entirely of cells with little extracellular matrix

specialized contacts

fits close together to form continuous sheets; adjacent cells are bound together by tight junctions and desmosomes

Polarity

All cells have an apical surface (free surface) exposed to the body exterior or the cavity of an interior organ, and an attached basal surface.

Most apical surfaces have what?

Microvilli: fingerlike extensions of the plasma membrane that increase the exposed surface area.

The basal surface is anchored by what?

A thin, supporting layer called the basement membrane

basement membrane

basal lamina + reticular lamina

Supported by connective tissue

all epithelial sheets rest upon and are supported by connective tissue

A vascular but innervated

No blood vessels in epithelial tissue. Must be nourished by diffusion from underlying connective tissues; are supplied by nerve fibers

Regeneration

As long as they receive adequate nutrition, epithelium can replace lost cells rapidly by cell division

Epithelial cells can be classified by

Shape and arrangement

Epithelial cells classification by shape are

Squamous, cuboidal, or columnar

Epithelial cells classification by arrangement are

Simple, stratified, and transitional

simple squamous epithelium

Description:

• Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm

• the simplest of the epithelia

Function:

• Allows materials to pass by diffusion and filtration in sites where protection is not important

• secretes lubricating substances in serosae

Location:

• Kidney glomeruli

• air sacs of lungs

• lining of heart, blood vessels, and lymphatic vessels

• lining of ventral body cavity (serosae)

simple cuboidal epithelium

Description: Single layer of cubelike cells with large, spherical central nuclei

Function: Secretion and absorption

Location: Kidney tubules; ducts and secretory portions of small glands; ovary surface

simple colmnar epithelium

Description: single layer of tall cells with oval nuclei; layer may contain mucus-secreting unicellular glands (goblet cells)

Function: absorption; secretion of music, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action

Location: non-ciliated type of the digestive tract, the gallbladder, and excretory ducts of some glands ciliated type line small bronchi, uterine tubes, and some regions of the uterus

pseudostratified columnar epithelium

Description: Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting goblet cells and bear cilia.

Function: Secretes substances, particularly mucus; propulsion of mucus by ciliary action.

Location: Nonciliated type in male's sperm-carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory tract.

stratified squamous epithelium

Description: Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers

Function: Protects underlying tissues in areas subjected to abrasion

Location: Nonkeratinized type of forms the moist linings of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry membrane.

stratified columnar epithelium

Description: Several cell layers; basal cells usually cuboidal; superficial cells elongated and columnar.

Function: Protection; secretion.

Location: Rare in the body; small amounts in male urethra and in large ducts of some glands.

stratified cuboidal epithelium

Description: Generally two layers of cube-like cells.

Function: Protection.

Location: Largest ducts of sweat glands, mammary glands, and salivary glands.

transitional epithelium

Description: resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar, surface cells dome shaped or squamouslike, depending on degree of organ stretch

Function: Stretches readily, permits stored urine to distend urinary organ

Location: lines the ureters, bladder, and part of the urethra

glandular epithelium

Composed of cells that are specialized to produce and secrete substances

A gland consists of one or more cells that make and secrete a product. This product, called a secretion, is a water-based fluid that often contains protein

Glands are classified according to two sets of traits:

Site of the product released and number of cells that form the gland

Site of the product released

Endocrine and exocrine

Endocrine

secreting internally

Exocrine

secreting externally

Number of cells that form the gland

Unicellular and multicellular

Unicellular

one celled

Multicellular

many celled

ducts

Tube-like connections to the epithelial sheets

Endocrine glands

Ductless glands that empty their hormonal products directly into the blood

examples: thyroid and pituitary glands

exocrine glands

secrete chemical substances into ducts that lead either to other organs or out of the body

unicellular exocrine glands

One celled; ex. Goblet cells

multicellular exocrine glands

composed of a duct and a secretory unit, classified by structure and mode of secretion; tubular, alveolar, or tubuloalveolar

Tubular

tubes

alveolar

Sacs

tubuloalveolar

alveolar + tubular

Modes of secretion

merocrine, apocrine, holocrine

merocrine glands

release watery secretory product via exocytosis with no loss of cell membrane. This includes salivary and sweat glands

apocrine glands

lose small portions of their glandular cell bodies during secretion

This includes mammary glands

holocrine glands

accumulate their products within them until they rupture

This includes sebaceous (oil) glands

muscle tissue characteristics

Contractile, well vascularized, and responsible for most types of body movement

types of muscle tissue

skeletal, smooth, cardiac

skeletal muscle tissue

found in muscles that attach to bones and is controlled by conscious effort; cells display striations (stripes) and multiple nuclei

smooth muscle tissue

also called nonstriated (visceral) or involuntary; no cross striations; found in blood vessels and other tube-shaped organs

cardiac muscle tissue

found only in the heart, striated, involuntary

nervous tissue function

Transmit electrical signals from sensory receptors and to effectors (muscles and glands) which control their activity

nervous tissue location

brain, spinal cord, peripheral nerves

Two types of cells

neurons and neuroglia

Neurons

the basic cells of the nervous system that allow different parts of the body to communicate with each other

composed of a cell body and 2 types of processes, axons and dendrites

Axons

Carry impulses away from the cell body

Dendrites

carry impulses toward the cell body

Neurogalia

Supports and bind components of nervous tissue, are designed for phagocytosis (eating of cells), and supply nutrients to neurons by connecting them with blood vessels

connective tissue general characteristics

Most abundant tissue type

Cells are farther apart than epithelial cells; contain matrix between cells

Major cell types of connective tissue

fibroblasts, macrophages, and mast cells

Fixed cells

Cells that remain in their place

wandering cells

Move through and appear in tissues temporarily, usually in response to an injury or infection

Fibroblasts

Most common fixed cell

Large star-shaped cell

Secrete fibers into extracellular matrix

Macrophages

wandering cell, phagocytic, important in injury or infection

mast cells

-fixed cell

-release heparin

-release histamine

Heparin

Anticoagulant

anticoagulant

blood thinner

Histimine

Makes capillaries leaky

Tissue fibers

produced by fibroblasts

Tissue Fiber Types

collagen, reticular, elastic

collagenous fibers

Strong and flexible connective tissue fibers that contain the protein collagen

elastic fibers

yellow connective tissue fibers that are not particularly strong, but can be stretched and will return to their normal shape when released

reticular fibers

very fine, short collagen fibers that branch to form a supporting network

types of connective tissue

loose adipose dense cartilage bone blood and hemopoietic

loose connective tissue

(also, areolar tissue) type of connective tissue proper that shows little specialization with cells dispersed in the matrix

adipose connective tissue function

acts as a storage depot for fat; provides insulation for the body

location of adipose tissue

beneath skin, around kidneys, behind eyeballs, on surface of heart and in joint areas

dense connective tissue

binds organs; tendons, ligaments, deeper layers of skin

SLOW IN REPAIR

cartilage connective tissue

chondrocytes (cartilage cells) ; rigid tissue which stands up to both tension and compression; avascular and lacks nerve fibers

3 types of cartilage connective tissue

hyaline, elastic, fibrocartilage

hyaline cartilage

Most common type of cartilage; it is found on the ends of long bones, ribs, and nose

elastic cartilage

ear flaps and larynx; more flexible than hyaline cartilage

Fibrocartilage

tough form of cartilage, made of thick bundles of collagen fibers embedded in chondroitin sulfate ground substance found in knees, between vertebrae, and in pelvic girdle

bone connective tissue

osteocytes embedded in a solid mineral matrix

blood connective tissue

Two parts; fluid and tissue

fluid in blood

-Transports a large variety of materials

-Assists in temperature regulation

-Aids in defense against disease

-Made up of plasma

tissue in blood

Blood flow

formed of red, white blood cells, and platelets

hemopoietic connective tissue

found in the red marrow cavities; responsible for formation of blood and lymphatic system cells; in spleen, tonsils, and lymph nodes

Epithelial membrane tissue types

Epithelium and connective

Epithelial tissue types

cutaneous, serous, mucous

cutaneous membrane

The skin; composed of epidermal and dermal layers

mucous membrane

Lines all body cavities that directly open to the exterior, such as the respiratory tract, and secretes mucus

serous membrane

the moist membrane found in closed ventral body cavities

named according to their site and specific organ associations, such as pleura, pericardium, and peritoneum

pleural cavity

contains the lungs

Pericardium

Membrane surrounding the heart

peritoneum

membrane that lines the abdominal cavity