AP - Tissues Overview - Chapter 4

Tissues

Tissues are groups of specialized cells and cell products that work together to perform specific functions

Histology

study of microscopic structure of tissues and cells; microanatomy

What are the 4 tissue types?

1. Epithelial tissue

2. Connective tissue (CT)

3. Muscle tissue

4. Nervous tissue

Epithelial Tissue

Function, Location, Distinguishing Characteristics

Function: protection, secretion absorption, excretion

Location: Cover body surfaces, cover and line internal organs, make up glands

Distinguishing: Lack blood vessels, cells divide, cells are tightly packed

Connective Tissue: Function, location, distinguishing characteristics

Function: bind, support, fill spaces, store fat, produce blood cells

Location: distributed through body

DC: are vascularized, cells are farther apart vs epithelial, have extracellular matrix

Muscle Tissue: Function, location, DC

Function: movement

Location: attached to bones, in internal organ walls, heat

DC: able to contract to stimuli

Nervous Tissue: Function, location, DC

Function: conduct impulses for coordination, integration, sensory reception

Location: brain, spinal cord, nerves

DC: cells communicate with each other and other body parts

Epithelia cover every _____ surface of your body.

exposed

What are the 4 main functions of epithelial tissue?

1. Physical protection (combat abrasion, dehydration, etc)

2. Control permeability

3. Sensation (large sensory nerve supply; seen in neuroepithelia in smelling, vision, balance, etc)

4. Secretions (through gland cells)

Epithelia Cellularity

• epithelia are comprised majority of cells

• minimal extracellular material

Epithelia Polarity

• apical and basal surfaces show polarity

• apical is top layer to open space

• basal layer is attached to basement membrane and is closer to CT

Epithelium Avascularity

• tissue lack blood vessels

• receive nutrients by diffusion/absorption

Epithelia Basement Membrane

• base of tissue is bound to basement membrane (BM)

• BM is made of successive layers

Epithelia Regeneration

• cells are continuously replaces through cell division

• happens at high rates

Epithelial sheets are supported by __________ _______.

connective tissue

What 3 factors maintain the integrity of epithelium barriers?

1. Intercellular connections (aka cell junctions)

2. Basement membrane attachment

3. Maintenance/repair

Cell Adhesion Molecules (CAMs)

• transmembrane proteins that bind to each other and help epithelial cells attach

Proteoglycans

• polysaccharide derivatives (GAGs/hyaluronic acid) that act as an intercellular cement

What are cell junctions?

Specialized areas of plasma membrane that attach cells to each other/ or extracellular stuff

What are the 3 types of cell junction?

1. Gap junctions

2. Tight/occluding junctions

3. Anchoring junctions

Gap Junctions are made of two interlocking _______ proteins. Each _______ is made of 6 ________ that make a cylinder channel. This channel exchanges ions, second messengers, etc. These junctions are important for cell _________ and cell growth.

• connexon

• connexins

• synchronization (muscle contractions)

connexon proteins

Tight/Occluding Junctions are formed by two membrane proteins, __________&________. They prevent water and ________ from passing between cells. This is a physiochemical separation. Can be found at the _______/

• claudins & occludins

• solute

• blood brain barrier

tight/occluding junction

Adhering Junctions are characterized by a continuous belt called the _______________ that circles and binds them to other cells _______. This makes _______ adhesion.

• zonula adherins

• cadherins

• lateral

adherins junction

Desmosomes are specially resistant to __________ stress. This includes stretching and twisting. Each of the two cells has a ________ area that is connected to the __________. The membranes are linked by __________.

mechanical

dense

cytoskeleton

desmoglein (cadherin protein)

desmosome

Hemidesmosomes/Anchoring Junctions connect filaments of the _________ into the basement membrane. They help increase adhesion to the _(2 words)__________.

• cytoskeleton

• basal lamina

hemidesmosome (anchoring junction)

What makes the basement membrane?

1. Basal lamina

2. Reticular lamina (dense layer)

Basal lamina is _______ to the epithelium and is clear. It contains _______ and functions to restrict ____________ movement to underlying CT.

• closer

• glycoproteins

• large molecule

The Dense Reticular layer contains coarse ______ fibers that give the basement membrane its strength. Dense layer acts as a _________________ between adjacent tissue and epithelium.

• protein

• diffusion filter

Epithelial cells continuously __________ through stem cells to combat chemical and physical disruption. The stem cells are located near the _________ for protection.

• divide

• basement membrane