2.75 Urine

Notes


Urine contains (excretion):

-> Salts (Affects composition of tissue fluid = osmoregulation)

-> Urea (Part of excretion of metabolic waste)

-> Water (Affects composition of tissue fluid = osmoregulation)

-> NO GLUCOSE


** Varies upon the conditions which a person is operating (environment/circumstances)

2.74 ADH

Notes


ADH = regulates water content of blood / control &alter composition of water in blood / more or less concentrated
--> Anti-diuretic hormone
--> Produced in hypothalamus
--> Flows through bloodstream --> kidney
**concentration must be right for osmoregulation (2.68b)

ADH targets collecting duct specifically
--> Collecting duct where water is selectively reabsorbed into bloodstream
--> ADH controls pores in the wall (more/less porous) to control 'flow' into bloodstream (more ADH ---> more porous)

Consequence of (more) ADH secretion
--> Urine more concentrated (more blood flows back into bloodstream)
--> Lower volume of urine

Questions?
ADH (hot day) = more ADH (more water available for sweat through the skin)
ADH (cold day) = less/no change ADH?
ADH (dehydrated) = more ADH (more water available for use in the body)

2.73 Glucose Re-absorption

Notes


Selective reabsorption of glucose occurs at PCT
--> Glomerula filtrate (glucose) ---reabsorption---> Blood stream

Filtrate contains:
-> Glucose
-> Water (collecting duct)
-> Salt
-> Urea

Urine = NO glucose? Due to filtration at PCT
--> Glucose is selectively reabsorbed (back into bloodstream) and taken out of the nephron system

2.72 Water Re-absorption

Notes


**Bowman's capsule = ultrafiltration ---> dissolved contents of plasma forced to become glomerula filtrate (water/salts/urea/glucose)

Filtration ---> filters out 'too much water' (as filtrate passes through nephron structure and reaches collecting duct)
---> Passing through collecting duct = water removed from filtrate (returned back to blood vessels/blood stream)
----> Water reselected to be reabsorbed into blood stream = 'selected reabsorption of water' occurs in collecting duct

2.71 Ultrafiltration

Notes


Nephron filters blood =
-> Filtered blood ('clean blood')
-> Excreted urine
----> Urine emerges from bottom of nephron (water / salts (NaCl,MgCl) / Urea (Toxic nitrogen waste)

How is urine formed? ULTRAFILTRATION (filtration of molecules)

1. Blood arrives into nephron through afferent arteriole (high blood pressure)
----> Blood vessel branches into coils (glomerulus)
----> Efferent arteriole (smaller diameter) = increase blood pressure flowing out (higher pressure)
**Glomerulus increases blood pressure

2. High pressure forces liquid in blood (plasma) into the inside of Bowman's capsule
----> Plasma contains:
-----------> water / salts / amino acids / glucose / urea)

----> Plasma inside capsule known as 'glomerula filtrate' (contains)

2.70 Nephron Structure

Notes


Process


Nephron = functional part of kidney (filtration/controlling composition of blood)

IN: Blood ---------- Renal artery (branch of aorta) --------> Nephron

OUT: Urine (excreted after filtration) <---- Ureter -------- Nephron

Urine collects in bladder for release
Filtered blood exits through renal vein ---> vena cava

Structure


-> Outer region = cortex {LIGHTER}
---> Inner region = medulla {DARKER}
--------> Inner space = pelvic region (where urine collects, drains down ureter)

**difference in colours = kidney is tubular structure made of tubes

Tube: starts on edge of medulla, moves outwards towards end of cortex, winds in cortex, dips down into medulla, back into cortex where winds again --> Dead end (Bowman's capsule)

Tubular structure (Nephron)

Twisted structure = convoluted tubules (tube)

Tube leading down to pelvic region (where urine is excreted) = Collecting ducts (tube)

Dip into medulla = loop of Henle

Dead end, cup shaped structure = Bowman's capsule

**tight knot of blood vessels (at Bowman's capsule) = glomerulus

* - - - u - - - /

1st convoluted tubule (- - -) = Proximal C.T. (PCT)

2nd convoluted tube (- - -) = Distal C.T (DCT)

---> Arrangement of nephron structure gives different colours of medulla & cortex

NOTE: millions of these structures (Nephrons) within a kidney.