3: Tissue Level Organization

Question 1

What is tissue?

Answer 1

A group of closely associated and structurally similar cells that perform a concerted function

Question 2

What is histology

Answer 2

The study of tissues, done by a pathologist

Question 3

What is extra cellular matrix

Answer 3

The substance found between cells, consists of ground substance and fibers. Connective tissue’s unique properties are based on the specific extracellular matrix characteristics of ground substance and fibres found in it

Question 4

What are the four basic tissue types, and what are they based on

Answer 4

Based on their structure and function, the four types are epithelial tissue, connective tissue, muscle tissue, and nervous tissue

Question 5

What are the general functions of epithelial tissue

Answer 5

Acts as a covering that lines hollow organs, cavities, and ducts, as well as external organs coverings, allows body to interact with internal and external environment. Also forms glands

Question 6

In regards to epithelial tissue, what does epithe mean

Answer 6

Laid on, covering

Question 7

What are the two general patterns of epithelial tissue

Answer 7

Surface covering and lining epithelium, and glandular epithelium

Question 8

Describe the extra cellular matrix of epithelial tissue

Answer 8

Epithelial tissue is highly cellular and therefore has virtually no extra cellular matrix

Question 9

Why is epithelial tissue considered to have polarity

Answer 9

Because it has an apical side and a basal side, apical is exposed free surface or edge, very specialized, some containing micro villi or cilia. The basal side is the lower attached surface, attached to the basement membrane structure

Question 10

depiction of structure of epithelial tissue

Answer 10

Question 11

What are the lateral surfaces found an epithelial tissue

Answer 11

The surfaces of the cells that fit close together to form continuous sheets, held together by specialized junctions between epithelial cells

Question 12

List the type of cell junctions that exist in general, and are found in most epithelial and some muscle and nerve cells

Answer 12

Tight junction, adhering junction, desmosome, hemi desmosome, and gap junction

Question 13

Give a very general overview of a tight cell junction

Answer 13

Web-like strands of transmembrane proteins fuse outer surfaces together. Found in lining of stomach, intestines, and bladder

Question 14

General overview of adhering cell junctions

Answer 14

Contain plaque inside plasma membrane which attaches to membrane proteins and microfilaments of cytoskeleton. Cadherins and plaque create adhesion belt. Helps epithelial cells resist separation such as in intestine as food moves through

Question 15

General description of desmosomes

Answer 15

Plaque, transmembrane proteins, attach cells but not to microfilaments, to intermediate filaments. Stability of cell and tissue. Spot-weld-like. Common in epidermidis, cardiac muscle fibers. Prevent cells from separating under tension. Similar to adhering but no belt

Question 16

General description of hemi desmosomes

Answer 16

Resemble desmosomes but don’t link to adjacent cells, looks like half a desmosome. Integrins instead of cadherins. Anchors to basement membrane, lamininin

Question 17

Brief description of gap junctions

Answer 17

Protein connections form fluid filled tunnels that connect neighbouring cells. Narrow spaces, ions and small molecules can diffuse from cell to cell. Found in embryos to regulate growth and for differentiation, enables nerve or muscle impulses to spread rapidly, affects lens and cornea of the eye

Question 18

What is the role of the basement membrane in epithelial tissue

Answer 18

It anchors the epithelial cells to the underlying connective tissue which acts as a support. Basement membrane is thin, extra cellular, and usually has two layers - basal lamina and reticular lamina

Question 19

Epithelial tissue has nerves but no blood supply, how does it survive

Answer 19

It is always found immediately adjacent to blood vessel rich connective tissue where requires oxygen, nutrients, and removes waste via diffusion

Question 20

What is epithelial tissues capacity for wound healing

Answer 20

High regenerative capacity, replaces lost cells readily

Question 21

List the general functions of epithelial tissue

Answer 21

Cover and line surfaces, form the secreting portion of glands, combine with nervous tissue to form organs for smell, hearing, vision, touch. Physical protection, regulation of absorption and transport of materials across membranes (filtration and absorption), excretory (urinary tract), secretory (enzymes, mucus, hormones), sensations through nerve endings

Question 22

How is epithelial tissue classified and named

Answer 22

According to the number of cell layers it has and it’s cell shapes. The first name of the epithelial tissue indicates the number of cell layers, and the second name indicates the shape of cells in the apical layer

Question 23

What are the three names that indicate the number of layers in an epithelial tissue

Answer 23

Simple- one layer of cells

Stratified - more than one layer of cells

Pseudo stratified - single layer that appears to be multiple layers due to misalignment of nuclei and some overlapping of cells

Question 24

In what cases do we usually find a simple layer in an epithelial tissue

Answer 24

When there is diffusion, osmosis, filtration, secretion, and absorption

Question 25

In what situations would be generally find a stratified layer of epithelial tissue

Answer 25

In cases where the underlying tissue needs protection from considerable wear and tear

Question 26

 What names are used to describe the shape of cells in the epithelium tissue

Answer 26

Squamous- resemble a tile on the floor Cuboidal look like cubes Columnar taller than they are wide, like columns Transitional cells - change to and from cuboidal and squamous in order to stretch 

Question 27

What is a strong suit of squamous cells

Answer 27

Because they are thin, they allow for rapid passage through

Question 28

Give some general points about cuboidal cells

Answer 28

They may have microvilli, and function in secretion or absorption

Question 29

Get some general points about the function of columnar cells

Answer 29

They protect underlying tissue, may have cilia or micro villi, and are specialized for secretion (mucous, enzymes, etc) and absorption (micro villi)

Question 30

What are the two special types of simple squamous epithelia

Answer 30

Endothelium which is synonymous to simple squamous epithelium, and mesothelium

Question 31

Where is endothelium found

Answer 31

The inner lining of hollow organs such as blood vessels and cardiac chambers, and lymphatic vessels. Lines cardio and lymph systems

Question 32

Where is mesothelium found

Answer 32

In the middle lining of certain body cavities such as peritoneal, plural, and pericardial (serous membranes-secretion). Also covers the visceral organs of those cavities, and can be found in air sacs of lungs, glomerular (Bowmans) capsule of kidneys, inner surface of tympanic membrane, and cornea.

Question 33

Found in areas that require diffusion and filtration, where are simple squamous epithelium are not found

Answer 33

In areas that experience wear and tear by mechanical strain

Question 34

Also functioning in secretion and absorption, where are simple cuboidal epithelium found

Answer 34

In kidney tubules, secretory portions of small glands (thyroid, mammary, salivary), ovarian surface, surface of capsule of lens of eye, forms pigmented epithelium at posterior of retina, ducts of some glands like pancreas

Question 35

Describe the role of ciliated simple columnar epithelium and where it’s found

Answer 35

Ciliary action can move sheets of mucus (ciliary escalator), and ciliated epithelium often contains goblet cells which secrete mucus. Line the small bronchi of the upper respiratory tract, uterine tubes (move oocytes to uterus) and uterus, some paranasal sinuses, central canal of spinal cord, and ventricles of brain.

Question 36

How do non-ciliated simple columnar epithelium differ from ciliated

Answer 36

They may have micro villi but not cilia. Non-ciliated simple columnar epithelium a line in the digestive tract from stomach to anus and it’s mucus lubricates and protects the stomach lining. Also found in gallbladder and ducts of some glands are. Higher level of secretion and absorption than cuboidal cells