Renal Flashcards
Renal system functions
- Removal of excess water
- Removal of wastes
- Regulation of electrolytes
- Regulation of pH
- Regulate blood pressure via the renin – angiotensin – aldosterone pathway
- Release the hormone erythropoietin
- Synthesise calcitrol (active form of vitamin D)
- Perform gluconeogenesis
Renal system consists of
- 2 kidneys – on posterior wall of abdomen
- 2 ureters - transport urine to bladder
- 1 bladder - stores urine
- 1 urethra - carries urine to outside
Processes within nephron
1) Filtration
2) Reabsorption
3) Secretion
Filtration
Pressure through net filtration in in glomerular capsule
Reabsorption
In proximal tubule, moving needed substances from nephron tubule in blood stream
Secretion
Everywhere but glomerular capsule, moving substances from blood in nephron tubule
Hormones affecting reabsorption
- ADH increases water reabsorption
* Renin-Angiotensin-Aldosterone increases water reabsorption
Atrial natriuretic
- Lower blood pressure
* Control electrolyte homeostasis
Micturition reflex
- Contraction of bladder and involuntary contraction of internal sphincter
- Controlled relaxed of the external sphincter allows urination to occur
Filtrate contains
Wastes, water, glucose, amino acids, electrolytes
Blood supply through kidneys
1) Aorta
2) Renal artery
3) Afferent arteriole
4) Glomerulus (capillaries)
5) Efferent arteriole
6) Peritubular
7) Renal vein
8) Inferior vena cava
Nephrons empty their products into
Collecting ducts, which drain into calyces, then the renal pelvis, then the ureter
Kidney structure
- An outer cortex
- A medulla made up of pyramids
- Calyces leading to a pelvis
Role of adipose tissue
- Protects the kidney
- Holds the kidney in place
- Acts as an energy (food) reserve
Nephron
Functional unit of the kidney
Each nephron consists of
• Renal corpuscle - glomerulus - glomerular (Bowman’s) capsule • Tubule - proximal tubule - loop of Henle (nephron loop) - distal tubule
Podocytes
Maximise the surface area for filtration
Net filtration pressure is
Blood hydrostatic pressure = 55 mmHg
Capsular pressure - 15 mmHg
Blood colloid osmotic pressure - 30 mmHg
Net filtration pressure =10mmHg
Proximal tube reabsorption
100% glucose and amino acids, 65% of the water, sodium and potassium, 80% of the bicarbonate
Loop of Henle reabsorption
50% of the water is reabsorbed
Distal tubule reabsorption
‘Fine tuned’ depending on the body’s requirements
Reabsorption takes place by
• Passive transport: no energy required - Diffusion - Osmosis • Active transport: energy required • Mediated: uses a protein carrier • Non mediated: no carrier molecule
Obligative water reabsorption
Water reabsorbed by osmosis (85%)
Facultative water reabsorption
Water selectively reabsorbed, regulated by ADH in the collecting duct
Reabsorption – Renin-angiotensin-aldosterone system
1) Stimulus - Low blood pressure
2) Receptors - Baroreceptors
3) Kidneys release renin
4) Activates angiotensinogen to convert to angiotensin
5) Angiotensin causes vasoconstriction and aldosterone release from adrenal cortex
6) Increases sodium reabsorption
7) Increases water reabsorption
8) Increased blood volume and narrower blood vessler increase blood pressure
Ureters transport urine to the bladder by
Peristalsis
Micturition
The expulsion of urine from the bladder
Micturition steps
- Bladder fills
- Stretch receptors fire
- Involuntary internal sphincter relaxes
- Voluntary external sphincter relaxes
Osmolarity
The number of solute particles dissolved
A high osmolarity
A high Na+ concentration and low water concentration.
A low osmolarity
A low Na+ concentration and high water concentration.
Antidiuretic hormone - Reabsorption
1) High sodium/high osmolarity
2) Osmoreceptors in hypothalamus detect dehydration
3) Stimulates posterior pituitary to release ADH hormone
4) Targets collecting ducts of kidneys to reabsorb water
5) Water reabsorption increases
6) Lower osmolarity
Negative feedback
