Lecture 4 - Epithelia

Question 1

What are the types of epithilial cell

Answer 1

Simple - one layer of cells
Simple Squamous 
Simple Columnar
Simple Cuboidal 
Pseudostratified

Stratified - Multiple layers of cells
Stratified Cuboidal
Stratified Columnar
Transitional
Non-keratinised Stratified Squamous
Keratinised Stratified Squamous

Question 2

Summarise simple Squamous epithelium

Answer 2

flat cells - 1 layer thick. good for diffusion

Gas exchange - alveolus, blood vessel endothelium
Barrier - bowmans capsule
secretion of lubricating fluid in the serous membranes

Question 3

Summarise simple Cuboidal epithelium

Answer 3

used for hormone synthesis, storage and mobilisation in the thyroid
absorption - Exocrine glands
Barrier - ovary
absorbtion and secretion - lines pancreatic and kidney ducts

Question 4

Summarise simple Columnar epithelium

Answer 4

they are long, you cam fit much more mitochondria, so are energetically active cells

Secretion into the gastric glands and intestinal mucosae
Absorption - small intestine, colon, gall bladder
Lubrication - Small intestine (the villi) and colon

Question 5

Summarise Pseusdostratified columnar epithelium

Answer 5

All cells are attached to the basal lamina, but not all cells reach the epithelial surface
used in respiration - nasal mucosa, trachea and bronchi
particle trapping and removing via the muco-ciliary escalator (will have cilia on the surface of the cells and mucus secreting goblet cells)

Question 6

Summarise Stratified Squamous Non-keratinised epithelium

Answer 6

No nucleus in surface cells sometimes, as not dividing cell
Protects against abrasion in the:

oral cavity
vagina
distal anal canal
oesophagus

Question 7

Summarise Stratified Squamous keratinised epithelium

Answer 7

the Skin epidermis
protects against abrasion
reduces water loss and entry significantly
barrier to pathogens and toxins
shields against uv damage
the top layers of cells are dead keratitinsed cells

Question 8

Summarise Trabsitional epithelium

Answer 8

Found on the surface if the bladder, and
urinary tract - (renal calcyes, ureters, bladder, urethra)

Protects against toxins and toxic chemicals
its distensible (stretchy) - allowing the bladder to fill and expand.

Question 9

Summarise Stratified cuboidal and columnar epithelium

these are less common

Answer 9

stratified cubodial - sweat gland ducts

stratified columnar - male urethra

Question 10

what is the mucous membrane structure?

Answer 10

the membrane lines internal tubes which open to the exterior in some way (UI, Respiratory and GI)

Made up of 3 layers
Epithelium - contains mucus secreting cells sometimes

Lamina Propria - adjacent layer of loose connective tissue attached to the basal lamina, it contains Immune cells, collagen fibrils/fibres produced by fibroblats and fibrocytes,elastin and reticular fibers, adipocytes, blood and lymph vessels, nerves and ground substance.
it connects epithelia to the muscaliris mucosa

Muscularis mucosa - a thin layer of smooth muscle, separates the mucosa from the submucosa,

in the GI tract beanth the submucosa the muscalris externa can provide 2 directions of contraction for peristalsis in the GI tract

Question 11

what is the structure of the serous membrane

Answer 11

a thin double membrane, that envelops viscera

made of

• mesothelium - simple squamous epithelium which secrets a thin film of lubricating fluid
• a thin layer of connective tissue attaching to epithelium of adjacent tissues

has an outer parietal serosa (outside surface)
an inner visceral serosa (inner surface)
inbetween the two layers is lubricating fluid of the serous cavity

the membrane promotes friction free movement of the viscera

the balloon example

Question 12

Epithelium - defenition and origin

Answer 12

Epithelium is
sheets of varied cells that cover the external surfaces of the body and line internal surfaces

they originate from all three embryological germ layers
ectoderm - epidermis
mesoderm - inner and outer lining of GI tract
endoderm - inner lining of body cavities

Question 13

summarise the structure and function of the epidermis

Answer 13

made of epithilial cells called karatinocytes
divide at basal lamina, move upward differentiating as they go, loose dividing ability
keratinocytes synthesise keratins, contribute to epidermis strength
transit time is 28 - 40 days
psoriasis - trasist time of 2-4 days, scaly cells

also contains melanocytes
hard to see histologically without special stains
produce melanin - skin colour
a lack of melanin give albinism

also conatins langerhans cells
again hard to see histologically
specialised to present antigens to t lymphocytes

Question 14

what are cell surface specialisations and their function?

Answer 14

Keratin - prevents water loss, protects against abrasion
cilia - controls micromovement
goblet cells
clara cells
microfold cells in small intestine
stereocillia - inner ear - respond to fluid motion for hearing and balance

Question 15

structure and function of goblet cells **

Answer 15

have microvilli on apical surface
release mucins through exocytosis
neuclues and ER and Golgi at bottom of elongated cell
top is full of secretory vesicles containing mucin

Question 16

what causes cystic fibrosis and what are the symptoms? **

Answer 16

Mutation in CTFR gene, a deficiency in the chloride ion give a sticky and immovable mucus

1) Airways - clogging and infection of bronchial passage -major cause of mortality
2) Liver - Blockage of the small bile duct
3) Pancreas - zymogen secretions not released
4) thick non motile stools in neo nates - needs surgery
5) reproductive tract - prevents semen transit and female infertility
6) malfunctioning swat glands in skin - salty crystally sweat

Question 17

structure and function of clara cells

Answer 17

club like structure
protect the bronchole epithelium by secreting protective products
detoxify harmful substances
they act as stem cells, differentiating into ciliated cells to regenerate bronchiolar epithelium

Question 18

structure and function of microfold cells

Answer 18

in the small intestine,
trap pathogens, to present to immune cells
main entry point for pathogens like salmonella

Question 19

how does smoking affect cell renewal rates

Answer 19

renewal rates
trachea -  1 - 2 months
alveoli - 8 days
goblet cells - 10 days
clara cells - never once die or undergo morphogenisis

smoking damages cilia and kills them, destroyes clara cells
thick mucus layer
scar tissue is layed down
carcinogens

Question 20

what are common condtions related to smoking?

Answer 20

-acute bronchitis - cough and mucus production for less than 3 months
-chronic bronchitis - chronic bronchi and bronchiole inflammation that produces a cough for 2 periods of 3 months or more in 2 years
reduces lung function, excess mucus in lung passages
start if irreparable damage to bronchioles and alveoli
-emphysema - destruction of the air sacs widens airspaces, larger alveoli with reduced elastic recoil
-COPD - chronic obstructive pulmonary disease - umbrella condition that includes emphysema and chronic bronchitis
-Asthma - wheeze, short of breath, airflow limitaiton, vary over time , triggered by cold, exercise, stress, ect
caused by bronchospasm, smooth muscle on bronchioles tighten, narrowing of airways