Tissues, Organs and System

Question 1

define tissue

Answer 1

a collection of cells that are adapted to a specific function

Question 2

define organ

Answer 2

two or more tissue combines to create a structural unit that has a particular function that is a sum of its parts.

Question 3

List three tissues not in organ systems

Answer 3

the ovum, spermatozoa and corpuscles in the blood( red & white blood cells and platelets)

Question 4

where are nerve cells derived from

Answer 4

ectoderm

Question 5

where are epithelial cells derived from

Answer 5

all three layers of the germ layer. the endoderm, mesoderm, ectoderm.

Question 6

where is mucosae derived from

Answer 6

endoderm

Question 7

where are muscle and connective tissue derived from

Answer 7

mesoderm

Question 8

describe how cells are held together at the molecular level

Answer 8

cell to cell adhesion molecules,
extrasolar matrix proteins(fibres)
internal-external scaffolding
close proximity ( pressure effects)

Question 9

list the epithelial cell adherence systems in the lateral surface?

Answer 9

tight junctions, adherens junctions,
desmosomes( adhering spot), gap junctions , cell adhesion molecules

Question 10

list the epithelial cell adherence systems in the basal surface

Answer 10

hemi- desmosome
focal adheasions
integrins
proteoglycans
cell adhesion molecules

Question 11

what cells do not have gap junctions?

Answer 11

spermatozoa, red blood cells and other motile cells.

Question 12

Difference between the major epithelial cell adherence systems in the basal surface,

Answer 12

hemi-desmosomes and focal adhesions attachment to basal lamina.
they both use integrins( that work as a alpha beta dimer)

however focal adhesion use intercellular actin filaments to attach to fibronectin through intern proteins. when attached there is conformational change that results in binding to collagen fibres

with hemi-desmosomes there is intracellular intermediate filaments of cytokeratin attached to laminin through integrins

Question 13

how do epithelial cells adhere to other epithelial cells

Answer 13

through cell surface proteins

Question 14

how do epithelial cells adhere to the basal lamina

Answer 14

through cellular adhesion molecules like the hemi desmosomes, focal adhesions, integrins protegylcans.

Question 15

how do epithelial cells adhere to muscle cells

Answer 15

connective tissue fibres

Question 16

what is the function of adherence proteins

Answer 16

to maintain the survival and structure of cells and therefore tissues.

to prevent pathogens from gaininng entry to the internal environment.

Question 17

define the mucosal membrane and its functions

Answer 17

the mucosal membrane is the moist inner lining of some organs and body cavities.

it stops pathogens and dirt from entering the body, prevents bodily tissue from becoming dehydratin, lubricate the surface.

Question 19

function of structure of the mucosa in the oesophagus

Answer 19

the oesophagus function is to provide passage from the oral cavity to the stomach.

its functional specialisations are
1- the epithelial cells are non keratinised stratified squamous cells.
2- scattered submucosal glands to provide lubrication
3- well developed muscularis external allows for organ return to original dimensions and peristaltic movement of food ( inner is circular, outer is longitudinal)

Question 20

function of the mucosa and what layers do what

Answer 20

the mucosa has three main functions,

1- lubrication
2- preventing dehydration
3-preventing pathogen ingress

it is made of three layers

epithelial cells,

lamina propria - contains specialised cells ( macrophages, lymphocytes, plasma cells, mast cells). it provides nutrition to the epithelium and immune protection.

muscularis mucosa contains no specialised cells and it folds the mucosal to increase surface area.

Question 21

what is the role of tight junctions

Answer 21

tight junctions prevent the movement of larger molecules through the outer layer/lumen into the deeper tissue layers of the organ.

located at the very top of the cell near the lumen/apical surface in the lateral border,

in the gut they can open to allow small molecules like sugar amino acids and water to cross to underlying tissues ( paracellular transport)

Question 22

what are adhesion junctions

Answer 22

specific to epithelial and endothelial cells. 1/3 of the distance from the luminal surface they function as a tissue stabilising factor and additional transport barrier. they are attached to the actin filament network

Question 23

what are the desmosome

Answer 23

the strongest of cell to cell adhesions, its tole is to provide mechanical strength and prevent tissue destruction. Intermediate filaments made of cyto-keratin fibres intracellularly and transmembrane inter cellularly.(between cells)

Question 24

how to distinguish between the small intestine and large intestine.

Answer 24

In the large intestine there are more goblet cells and less villi

Question 25

define epithelia

Answer 25

epithelia are sheets of contiguous cells, of varied embryonic origin, that cover the external surface of the body and line many internal surfaces.

Question 26

function of the gastrointestinal mucosa and how the structure of the constituent tissue is related to this

Answer 26

the function of the gastorintestinal mucosa is to absorb nutrients, protect from pathogen ingress and move contents and expel waste. the microvilli on the epithelia allow effienient transport and absorption when a peristaltic movement is propagated form the muscularis external.