6 Markers

Question 1

Describe similarities and differences between the ultrafiltration in kidneys and the formation of tissue fluid.

Answer 1

Similarities:
- both occur in the capillaries
- small molecules filtered out of blood
- large molecules such as proteins are too big to diffuse out
- high hydrostatic pressure
- many molecules such as water and sugar are re absorbed into capillaries

Differences:
- bowman’s capsule vs species in between cells
- in kidneys, molecules not re absorbed leave the body in urine while in tissue fluid, what is not reabsorbed forms lymph
- blood filtered through 3 layers vs one

Question 2

Describe how endocrine and nervous system work together to increase re absorption of water in collecting duct.

Answer 2

The nervous system:
Osmoreceptors in hypothalamus detect low water potential in blood, ADH is produced in hypothalamus, and released in posterior pituitary which is an extension of hypothalamus. Negative feedback

Endocrine:
Release of ADH from posterior pituitary into blood and release of aldosterone from adrenal medulla.

ADH bind to receptor in cell membranes of collecting duct and increases permaebility to water

Aldosterone:
Sodium ions pumped out of collecting duct, lowering w.p of tissue fluid in medulla, conc gradient established, water diffuses out via osmosis