Unit 4 Flashcards
What are the two fluid compartments of the body and what do they contain?
Intracellular – within the cells
Extracellular – tissue, plasma, lymph, transcellular fluid
Total body water is contained
What is the ratio of body fluids?
Intracellular = 2/3 Extracellular = 1/3
If total body water amounts to 40L
25L= intra
15L = extra
What are the 7 functions of the kidney?
- maintenance of water balance
- maintenance of electrolyte balance
- maintenance of blood pH
- removal of wastes and toxins
- gluconeogenesis
- hormone production
- urine production
What is gluconeogenesis?
- Making glucose from non glucose
* During prolonged periods of fasting the kidneys make glucose from amino acids and other precursors (lactic acid)
What is the main function of the urinary system?
Control the internal environment of the body by controlling the composition of the blood.
Blood must always be in equilibrium with other body fluids
What hormones are produced directly by kidney?
Erythropoietin
• Stimulates red blood cell formation in red bone marrow
• Stimulus for production = decrease of oxygen in blood
• Encourages multipotent stem cells to become erythrocytes (RBC’s)
What is active vitamin D?
- Indirect hormone production
- Result of action of UV light against skin
- 2 hydroxyl groups are added by liver and kidney
- Results in molecule that stimulates absorption of calcium from GI tract
What is aldosterone?
- Indirect hormone secretion by adrenal gland in response to renin secreted in kidney during low bP.
- Renin = enzyme produced by kidney in response to decreased Bp
Summarise the aldosterone pathway (7 steps)
- low bP
- renin production (kidney)
- production of angiotensin 2
- aldosertone secretion (adrenal gland)
- inc absorption of Na+ & H20 in kidney tubules
- blood volume inc
- blood pressure inc (to normal)
What is a nephron?
The functional unit of the kidney, they do the kidneys job (filter blood and produce urine)
About 1 million per kidney
What are the main parts of the nephron?
- Renal corpuscle (consists of glomerulus and bowmans capsule)
- Proximal convoluted tubule
- Loop of henle
- Distal convoluted tubule (2-4 make up renal tubule)
- Collecting duct
What are the two layers of the bowmans capsule?
What is the bowmans space?
• Outer parietal layer
Inner visceral layer (in contact w glomerulus)
• The space between the parietal and visceral layers
What is the filtration barrier?
What is its function?
The barrier between the blood flowing through the glomerulus and the filtrate in the bowmans capsule.
Filters water and small solutes from blood plasma into renal tubule as the 1st step in urine production. Large molecules not filtered, remain in blood
What are the 3 layers of the filtration barrier?
- glomerular capillary endothelium
- basement membrane of glomerulus
- epithelium of visceral layer of bowmans capsule
What is the difference between the glomerulus and normal capillaries?
- Much longer, larger surface area
* More permeable so has higher rate of filtration
What is the function of the renal tubule and what are the 3 main parts?
What is the collecting duct function?
Function: reabsorption and secretion of substances
- PCT
- nephron loop/loop of henle
- DCT
Receive filtrate from many nephrons
What are the 3 protective layers of the kidney?
- renal capsule
- adipose capsule
- renal fascia
What are the two capillary networks in the nephron?
- glomerulus
- peritubular capillaries/vasa recta
at all points the renal tubule is intimately associated with the peritubular capillary network to allow transfer of materials between peritubular blood and lumen of tubule.
What is the structure and function of juxtamedullary nephrons?
- make up 15% of nephrons
- longer loop of henle, extends to medulla (inner).
- has vasa recta (blood capillaries around loop)
- involved in concentrating and diluting urea
What is the hilus/hilum?
The indentation on one side of the kidney where the ureters and blood vessels enter and leave kidney
Blood supply is mainly to the cortex as that is where filtration occurs
What amount of cardiac output do kidneys receive?
Which vein /artery carries blood to and from the kidneys?
25% which is approx. 1200ml of blood per minute
Renal artery = into
Renal vein = away from
What is unusual about the blood flow in kidneys compared to normal blood flow?
In kidneys blood flows through two capillary networks.
Afferent arteriole glomerulus efferent arteriole peritubular capillaries/vasa recta
What is an important feature of blood flow in the kidney that contributes to the high rate of filtration?
High blood pressure that exists at nephron.
Occurs due to a pressure build up because of narrower efferent arteriole (compared to wider afferent arteriole) carrying blood away from the kidney.
What are the 3 stages of urine production?
- glomeruler filtration
- tubular reabsorption
- tubular secretion
What is glomerular filtration?
- passive process where water and solutes in blood move across wall of glomerular capillaries into bowmans space and then to renal tubule.
- Non-specific. Size of molecule is only factor (less than 5nm)
What is the Glomerular Blood Hydrostatic Pressure?
The pressure in blood flowing through the kidney providing the force for filtration to occur (usually 60mm/Hg)
What are the 2 main pressures opposing GBHP?
- Hydrostatic pressure - from fluid already in bowmans space (15mm/Hg)
- Osmotic pressure - due to proteins etc in plasma (27mm/Hg)
What is Net Filtration pressure?
The net force of hydrostatic pressure of blood flowing through the glomerulus.
Calculated by GBHP –
(Hydrostatic + osmotic pressure)
If net force drops, so does filtration
What is tubular reabsorption?
- Allows indiscriminately filtered small substances to be reabsorbed back into body. Specific and selective. Active and pass.
- 99% of daily 180L of filtrate goes back into blood by flowing through peritubular caps/vasa recta
what are some substances that are usually reabsorbed by tubular reabsorption?
- Water
- Nutrients (glucose, amino acids)
- Ions
Selective reabsorption goes from tubule to blood.
What is tubular secretion?
When substances are added to the filtrate by active transport in the reverse direction to reabsorption. Removes excess substances from body and regulate blood pH.
Goes from blood to tubule
Where does tubular secretion take place and what are some commonly excreted substances?
- PCT, loop of henle, CD
- Is an active process
- Substances include H+ ions, K+ ions, drugs like penicillin
What allows for reabsorption in renal tubule?
What are the two types of reabsorption?
- Closeness to peritubular caps
- Epithelial cells of renal tubule
- Microvilli covering PCT
- Obligatory – not dependent on body needs
- Facultative – dependent on body needs
What types of control are involved in Na+ reabsorption?
region of nephron, transport mechanism, hormone involved
- Obligatory = PCT, ascending Nephron loop
- Facultative = DCT and CD
- Active transport
- Aldosterone hormone
What types of control are involved in H20 reabsorption?
region of nephron, transport mechanism, hormone involved
- Obligatory = PCT, descending Nephron loop
- Facultative = CD
- Osmosis
- Antidiuretic ADH
What types of control are involved in Cl- reabsorption?
region of nephron, transport mechanism, hormone involved
- PCT, ascending loop
- DCT and CD
- Passive electrostatic attraction
- No hormone
What types of control are involved in HCO3- reabsorption?
region of nephron, transport mechanism, hormone involved
- PCT& DC
- Electrostatic attraction in response to Na+ reabsorption
- No hormone
What types of control are involved in K+ reabsorption?
region of nephron, transport mechanism, hormone involved
- PCT, ascending loop (reabsorption)
- DCT, CD (secretion)
- Passive – in response to Na+ reabsorption in PCT
- Active – reabsorption in loop
- Active – secretion in DCT and CD
- Aldosterone hormone
What types of control are involved in Glucose reabsorption?
region of nephron, transport mechanism, hormone involved
- PCT
- Active
- No hormone
What types of control are involved in Urea reabsorption?
region of nephron, transport mechanism, hormone involved
- PCT and CD
- Diffusion (passive)
- ADH coupled with water reabsorption
What is micturition?
Act of expelling urine from the urinary bladder aka urination
What are the 3 layers of the ureters?
- mucosa – transitional epithelium
- muscularis – longitudinal and circular layers
- adventitia – fibrous connective tissue
Ureters transport urine from kidney to bladder
What are the 3 layers of the urinary bladder?
- mucosa – epithelial layer
- muscularis – thick muscle layer (detrusor muscle)
- Adventitia – all around bladder except superior surface that is in contact with peritoneum (covered in serosa)
What is the trigone?
Smooth triangular region at base of bladder.
Posterior two corners are opening of ureters
Third corner is opening to urethra
What is detrusor muscle and its purpose?
- Muscular layer in bladder
- 3 layers of smooth muscle fibres (inner and outer longitudinal, middle circular layer)
- Allows squeezing action
- Involuntary control
What is the urethra?
- Thin walled muscular tube that drains urine from bladder
* Guarded by internal (involuntary, smooth muscle)and external (voluntary, skeletal muscle) sphincter
What occurs during the process of micturition?
- When 200-400ml of urine is present, stretch receptors are stimulated
- Micturition is a spinal reflex, influenced by higher centres of brain
- Reflex causes contraction of detrusor muscle, dilation of internal sphincter
What are 3 ways the kidney can raise blood pH if required?
- secreting H+ ions in filtrate /urine
- reabsorbing filtered HCO3- ions
- creating new HCO3- ions
What are the buffer systems related to the renal system?
- bicarbonate/carbonic acid system – control pH of body fluids
- Phosphate buffer system – control pH of urine
What are the 6 physical characteristics of normal urine?
- volume – 1-2L in 24h
- colour – yellow to amber
- turbidity
- odour
- pH – 4.6-8.0
- Specific gravity – density 1.001-1.035
What are 7 abnormal constituents of urine?
- glucose
- proteins
- ketone bodies
- haemoglobin
- bile pigments
- erythrocytes
- leukocytes
In urine what are the origins of:
- water
- urea
- creatinine
- uric acid
- fluid, food, metabolic activities
- deamination of amino acids
- breakdown of creatinine phosphate
- breakdown of DNA/RNA
In urine what are the origins of:
- sodium ions
- potassium ions
- ammonium ions
- major extracellular ion, derived from metabolic activity and intake
- major intracellular ion and same as above
- protein catabolism and glutamine deamination in kidneys
