Tissues

Tissue

A group of similar cells that perform the same function.

Histology

study of tissues

What are the four types of tissues?

epithelial, connective, muscle, nervous

epithelial tissue

Sheets of tightly packed cells that line organs, body cavities, and body surface. Also known as epithelium.

What are two forms of epithelial tissues?

covering and lining epithelia, glandular epithelia

What is glandular epithelium?

secretory tissue in glands

Example of glandular epithelium

salivary glands

What is the covering and lining epithelia?

on external and internal surfaces

Example of covering/lining type of epithelium

skin

Main Functions of epithelial tissues

protection, absorption, filtration, excretion, secretion, sensory reception

Structural features of epithelial tissue

Polarity, Specialized Contacts, Supported by Connective Tissues, regenerative, avascular but innervated

What are the specialized Contacts in the epithelial tissue?

Tight junctions, desmosomes, gap junctions

What is a tight junction?

Prevents substances from leaking across epithelial layer? It is like sewing

What is a desmosome?

Prevents adjacent cells from pulling apart. Ex. Velcro straps

What are gap junctions?

Small tunnels that connect cells, facilitating the movement of small molecules and ions between the cells.

What is polarity in the epithelial tissue?

apical surface and basal surface

What are apical surfaces?

Borders open space; smooth

What is the basal surface?

attached to the underlying basal laminate and next to the underlying connective tissue

What does the basement membrane consist of?

basal lamina and reticular lamina

What is the basement membrane?

Connective tissue reinforcing all epithelial sheets. It resists stretching and tearing.

Why is it so dangerous for epithelial cells to break through the basement membrane?

Breaking through basement membrane is a feature of skin cancers

What is avascular

no blood vessels

How is the epithelial tissue nourished?

by diffusion from underlying connective tissues

What is innervated

supplied by nerve fibers

Two types of layers in epithelia

Simple and stratified

What is a simple layer

single layer of epithelial cells

What is a stratified layer?

multiple layers of epithelial cells

What are the three types of epithelial cells?

squamous, cuboidal, columnar

What is the function of simple squamous epithelium?

Allows materials to pass by diffusion and filtration sites

What is the second function of simple squamous epithelium

Secretes lubricating substances in serosae

Where is simple squamous epithelium found?

lungs, kidneys, blood vessels, and lymphatic vessels, serosae

What does simple squamous epithelium look like?

single layer of flat cells

What does the simple columnar epithelium look like?

Single layer of tall cells

What is the function of simple columnar epithelium?

Absorption, secretion of mucus, cilia to move substances over epithelial surface

Where is simple columnar epithelium found?

digestive tract, gallbladder, ducts of some glands, bronchi, and uterine tubes

What does the pseudostratified columnar epithelium look like?

Single layer of cells of different heights, some not reaching free surfaces

What does the pseudostratified columnar do?

Mucus secretion, movement of mucus by sweeping action of cilia on apical surface

Where is the pseudostratified columnar epithelium found?

Upper respiratory tract, ducts of large glands, and tubules in testes

What does the Stratified squamous epithelium look like?

Thick epithelium composed of several cell layers. Apical surface is squamous, deeper layers are often cuboidal or columnar

What is the stratified squamous epithelium function?

Protects underlying tissues in areas with lots of wear-and-tear

Where is the stratified squamous epithelium located?

Near keratinized areas in the skin and in non-keratinized areas in moist linings like back of the throat.

Which classes of the epithelia are very rare?

Stratified cuboidal and stratified columnar epithelium

What is the stratified cuboidal epithelium

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

What is the stratified columnar epithelium

Function: protection and secretion Location: rare in the body; small amounts in male urethra and in large ducts of some glands

Where is transitional epithelium found?

lines the ureters, urinary bladder, and part of the urethra

What does the transitional epithelium look like?

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

What does the transitional epithelium do?

allows the urinary organs to expand and stretch; cells change shape when stretched

What is a gland?

One or more cells that makes and secretes an aqueous fluid called a secretion

What is glandular epithelium?

composed of cells that produce and secrete substances into ducts or body fluids

What is the multicellular epithelial gland?

Form by inward growth of an epithelial sheet.

What are the two types of glands?

exocrine glands and endocrine glands

What does the exocrine gland do?

secretes substances (oil, saliva, sweat) into ducts (tiny tube) then the substance will empty onto the body surface or into an opening inside the body (lumen)

Example: oil glands of skin, Salivary glands, mucus, oil, sweat

What does the endocrine gland do?

secrete hormones into tissue fluid or blood

Example: adrenal glands, ovaries, testes

What is muscle tissue?

Tissue that has the ability to contract or shorten. Voluntary muscle (skeletal) and involuntary muscle (smooth muscle and cardiac muscle). Responsible for body movements

Three muscle types?

skeletal, cardiac, smooth

What does the skeletal muscle look like?

long, cylindrical, multinucleate cells; obvious striations;multiple nuclei per cell

What does the skeletal muscle do?

It produces voluntary movement

Where is the skeletal muscle located?

attached to bones and skin

What does the cardiac muscle look like?

Branched cells, obvious striations, 1-2 nuclei per cell

What does the cardiac muscle do?

Contracting heart & propelling blood; involuntary movements

Where is cardiac muscle located?

heart

What does the smooth muscle look like?

Cells are spindle shaped, no striations, cells arranged closely to form sheets

What does the smooth muscle do?

Propels substances or objects along internal passageways; involuntary control

Example: urine, baby, foodstuffs

Where is smooth muscle located?

blood vessel walls and walls of hollow organs

What is the nervous tissue?

main component of the nervous system, helps regulate and control body functions

Where is nervous tissue found?

brain, spinal cord, nerves

Which tissues regenerates poorly?

Cardiac muscle and nervous tissue

Which tissues regenerate a moderate amount?

Smooth muscle and dense regular connective tissue

Which tissues regenerate easily?

Bone, epithelia, dense irregular connective tissue, blood-forming tissue, areolar connective tissue

What is the cutaneous membrane?

The skin, a dry membrane with a keratinizing epithelium (the epidermis).

What are the two layers of the cutaneous membrane?

Epidermis: keratinized stratified squamous epithelium

Dermis: thick layer of connective tissue

What is the mucous membranes?

Lines body cavities that are open to the exterior; bathed by secretions or urine

What are the two layers of the mucous membrane

Epithelial sheet and lamina propria (loose connective tissue)

What is a serous membrane?

Line body cavities that are closed to the exterior

What are the layers of the serous membranes?

Thin areolar connective tissue and simple squamous epithelium

What are the the two types of repair for tissues

Regeneration and Fibrosis

Regeneration

Same kind of tissue replaces destroyed tissues, so original function is restored

Fibrosis

Connective tissue replaces destroyed tissue, and original function lost

What are the three step of repair

Inflammation

Organization

Regeneration

Tissues that regenerate extremely well

Epithelial tissues, bone, areolar connective tissue, dense irregular connective tissue, blood-forming tissue

Tissues that regenerate moderate amount

Smooth muscle and dense regular connective tissue

Tissues that regenerate poorly

Cardiac muscle and nervous tissue

Primary Germ Layers

Ectoderm mesoderm endorm

What does Blood Tissue look like?

Red and White blood cells un fluid matrix

What is the function of blood tissue

Transports gases, nutrients, wastes, etc

Where is Blood tissue located

Within blood vessels.

Is the Bone innervated

Yes is is innervated, containing neerves

What does the bone store

Calcium and fat

Is the bone highly vascular

Yes, it is highly vascular

What are the individual structural units of bones

Osteons

What does the bone tissue look like

Looks like the inside of a tree, hard calcified matrix, many collagen fibers, osteocytes in lacunae

What is the functions of bone tissue

Supports and protects, stores calcium, minerals and fat, provides levers for locomotion.

Where is the site of blood cell formation

Bone tissue

Where is the bone tissue located

In the bones

What does the areolar tissue look like

Gel-like matrix, collagen, elastic, and reticular fibers, fibroblasts, macrophages

What is this a picture of

Areolar connective tissue

What is the function of areolar tissue

Cushions and protects organs, holds and moves tissue fluids

Where is areolar connective tissue found

Distributed under epithelial layers

What is this a picture of

Adipose tissue

What is this a picture of

Reticular tissue