Histology

Question 1

How many types of muscle are there in the human body?

Answer 1

3

Cardiac, skeletal and smooth

Question 2

What is cardiac muscle and what are the structural properties?

Answer 2

Type of muscle in heart.
Branched cylindrical
1 centrally located nucleus
Striations
Large diameter, 10-20 micrometres
Small length, 50-100 micrometres

Question 3

What is smooth muscle and what are the structural properties?

Answer 3

This is found in the walls of blood vessels, airways and in the viscera (internal organs in main cavity of body)

Fusiform (spindle-shape)
1 centrally located nucleus
No striations
Small diameter 3-8 micrometres
Medium size 30-200 micrometres

Action is involuntary and controlled by ANS and endocrine system

Question 4

What is skeletal muscle and what are the structural properties?

Answer 4

AKA striated/voluntary muscle - attached to bones
Long cylindrical 
Many peripherally located nuclei 
Striations
Very large diameter 10-100μm
Very long length 100μm-30cm

Question 5

How does skeletal muscle separate muscles?

Answer 5

Into

• Endomysium - innermost layer, covers outside of each individual muscle fibre
• Perimysium - covers outsides of bundles of muscle fibres called Fascicles
• Epimysium - outermost layer that covers the outside of a muscle; continuous with the Fascia

Question 6

What is the fascia?

Answer 6

Dense connective tissue whose job is to surround muscles and other structures, the fascia that is associated with muscles is called the deep fascia

Question 7

What is a motor unit?

Answer 7

A single motor neuron and all of the muscle fibres that it innervates

Question 8

What are the striations in cardiac and skeletal muscle a result of?

Answer 8

Myofibrils within the myocytes - the cylindrical structures that allow for contraction to take place

Question 9

What is the basic repeating segment of the myofibril?

Answer 9

The sarcomere, consist of:

• Darker areas - thick filaments (myosin)
• Lighter areas - thin filaments (actin)

These filaments overlap which is why they’re able to contract

Question 10

What is the difference between tendon and ligament?

Answer 10

Tendons may also attach muscles to structures such as the eyeball. A tendon serves to move the bone or structure. A ligament is a fibrous connective tissue which attaches bone to bone, and usually serves to hold structures together and keep them stable.

Question 11

What is the A band?

Answer 11

Span the entire myosin content of a single sarcomere, making up the darkest area of the sarcomere

Question 12

What is the M line?

Answer 12

This lies in the middle of the A band, this is the middle of the sarcomere where the myosin filaments attach onto

Question 13

What is the H zone?

Answer 13

Area of sarcomere where there is myosin but no actin, this space decreases when the muscle is contracting and the sarcomere condenses

Question 14

What is the I band?

Answer 14

Area comprised of just actin, lightest part of sarcomere, this also decreases in length when muscle contracts

Question 15

What is the Z line or Z disc?

Answer 15

Defines borders of sarcomere, Z line also conincides with the position of the intercalated discs of the cardiomyocytes

Question 16

How are intercalated discs associated with cardiac muscle?

Answer 16

Cardiac muscle cells are joined by intercalated discs, these coincide with the Z lines of the sarcomeres, they allow waves of depolarisarion to spread amongst the cardiomyocytes which allows for simultaneous contraction

Question 17

What is dystrophy and myopathy?

Answer 17

Dystrophy - muscle wasting disease due to progressive degeneration of muscle fibres

Myopathy - Any disease of the muscle that leads to weakening of the muscle

Question 18

What is muscular atrophy?

Answer 18

Wasting away of muscles due to decrease in myocyte size (due to decrease in number of myofibrils), can come as a result of disuse or denervation.

Question 19

How is the mucosa of the stomach different to oesophagus histologically?

Answer 19

Oesophagul mucosa - light pink
Gastric mucosa - Darker red
4 ordinary layers of tissue present (mucosa, submucosa, muscularis externa and adventitia)
Stomach has LCO muscle
Oesophagus only has LC
Stomach - contains RUGGAE - folds in SA to increase absoprtion
Gastric mucosa also has surface pits which contain glands

Question 20

How is the epithelia of the stomach vs oesophagus?

Answer 20

Oesophagul epithelium will go from stratified squamous to simple columnar in gastric epithelium

N.B Barrett’s oesophagus is dysplasia of oesophageal epithelium which turns oesophageal epithelium from stratified squamous to simple columnar

Question 21

What are the secretory cells of the gastric glands?

Answer 21

Parietal cells - Hcl, Intrinsic factor, appear large and pink with central nucleus

Chief cells - Lipases, pepsinogen - activated by Hcl to form pepsin (protease), basally located purple nuclei

Goblet cells - mucous
Appear as simple columnar epithelium containing many granules near apex

Question 22

What is the difference between adventitia and serosa?

Answer 22

In the abdomen, whether an organ is covered in adventitia or serosa depends upon whether it is peritoneal or retroperitoneal

Intra - serosa
Retro - adventitia

Question 23

What are intraperitoneal organs?

Answer 23

Stomach
Bulb of duodenum, ileum, jejunum
Transverse and sigmoid colons
Spleen 
Liver

Covered in serosa

Question 24

What are the retoperitoneal organs?

Answer 24

All of dudoenum bar bulb 
Caecum
Ascending and descending colon
Pancreas
Kidneys

Covered in adventitia

Question 25

How do you tell difference between PCT and DCT?

Answer 25

PCT - longer, thus more found in cortex, lumen uneven, contains single layer of cuboidal cells, luminal cells have microvilli (brush border)

DCT - shorter, therefore few in cortex, lumen often large, lined by simple cuboidal cells, cytoplasm stains less intensely, cells lack microvilli

Question 26

What are the white areas within the renal corpuscle?

Answer 26

Capillary loops