Histology

Question 1

T-tubules

Answer 1

T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the centre of skeletal and cardiac muscle cells.
Their role is to maintain the SR(sarcoplasmic reticulum) calcium store under the tight control of membrane depolarization

Question 2

SR

Answer 2

sarcoplasmic reticulum
The sarcoplasmic reticulum (SR) is a membrane-bound structure found within muscle cells that is similar to the endoplasmic reticulum in other cells.
important in transmitting the electrical impulse as well as in the storage of calcium ions. These longitudinal tubules form a membrane-bound system of tubules and cisterns that surround the myocytes.

Question 3

Bronchus >< bronchiole

Answer 3

The amount of cartilage in the walls of the bronchi gradually decreases and disappears after the point where the bronchi divide into smaller airways called bronchioles.

Question 4

Endothelial cells

Answer 4

line the internal surfaces of the components of the circulatory system