Urinary System Flashcards
what are the urinary organs?
kidneys, ureters, bladder and urethra
write a short note on the kidneys
location: either side of the vertebral column under the diaphragm.
structure: bean shaped, red/brown, fist size. covered in connective and adipose tissue
describe the structure and location of the ureters
Extend from kidney to bladder. Small muscular tubes which are 25cm in length, 5-7mm diameter. Consist of smooth muscle. Peristalsis occurs here. Lined by transitional epithelium, underlying connective tissue, muscularis and adventia (fibrous layer with blood vessels)
what is the Hilum
where the renal artery enters the kidney, and the renal vein and ureters exit the kidney
write a note on the bladder
Balloon shaped. Thin and transparent. Holds 400-600mls urine. Has 2 sphincters where urethra exits.
write a sentence on the urethra
extends from bladder to outside. 4 cm in length in women, 20cm in men
what are the 4 functions of the kidneys
excretion of metabolic waste. maintenance of salt/water balance. pH maintenance. hormone secretion
what wastes are excreted by kidneys
Nitrogenous waste:
1. urea ( formed in liver - ammonia + CO2)
2. Creatinine: produced by creatine phosphate in muscles
3. Uric acid: nucleotide metabolism waste (purines). Uric acid dissolves in blood and is filtered by kidneys
explain the water/salt balance function of kidneys
Salt balance influences blood volume as water follows salt. So, increased salt in blood = increased blood volume. A higher blood volume then = hypertension. Kidneys regulate the amount of ions in blood
How do the kidneys maintain pH
Blood should be pH of 7.4. Kidneys excrete H+ and reabsorb HCO3- to maintain pH
What hormones are secreted by the kidneys?
Renin which stimulates aldosterone secretion which reabsorbs sodium ions.
Erythropoietin: stimulates RBC production.
What relationship do the kidneys have with vitamin D
They activate vitamin D. This vitamin activates calcitrol which promotes Ca2+ absorption in the digestive tract.
What are the three regions of the kidney?
cortex, medulla and pelvis
what is a nephron?
an independent urine forming unit
function of renal artery?
oxygenated blood to kidneys
function of afferent and efferent arterioles?
afferent: blood to glomerulus which supplies the nephrons.
Efferent: blood away from glomerulus
function of peritubular capillaries?
supplied by efferent arteriole. travel along nephrons and allow reabsorption and secretion between blood and inner lumen.
They surround the proximal and distal tubules and the loop of Henle (called vasa recta here)
function of renal veins?
carry filtered blood away
what are the functions of the nephrons
- initial filtration of blood
- selective re-absorption of filtered substances back into blood
- secretion of unwanted substances
the nephron has two components, what are they?
tubular and vascular
what are the parts of the tubular component
Bowmans capsule, Proximal convoluted tubule (PCT), Loop of Henle, Distal convoluted tubule (DCT), collecting duct
write a note on Glomerular (Bowmans) capsule
located at the beginning of tubular component of nephron. Performs first step of blood filtration. Glomerulus is enclosed in a sac.
Outer layer: squamous epithelium
Inner layer: made of podocytes (long cytoplasmic extensions)
Allow the passage of materials but not blood (aka glomerular filtration)
write a note on the Proximal Convoluted Tubule (PCT)
This is beside glomerulus. Lined with cuboidal epithelium. Has microbilli for increased surface area for filtrate absorption. Cells of PCT have many mitochondria for active transport energy
write a note on the function and structure of the Loop of Henle
This can be divided into descending and ascending limbs.
Epithelium lining has special filtration abilities that can re-absorb water and concentrate the filtrate.
where does the ascending limb of the loop of henle deliver fluid to?
distal convoluted tubule
Write a note on the Distal convoluted tubule
Is lined by cuboidal cells with no microvilli
This tubule is important for active secretion of ions and other materials. Also reabsorbs sodium ions from urine. Toward the end of the DCT, osmotic flow of water helps to concentrate the urine
explain the structure and function of the collecting ducts?
the distal convoluted tubule (DCT) opens into a collecting tubule that is lined by simple cuboidal epithelium. The collecting tubules can reabsorb sodium and retain passive water.
Groups of these collecting tubules open into a collecting duct that descends into the medulla. The ducts allow passive water movement into interstitial fluids. The lining cells can secrete H+ ions into lumen
what 3 processes take place in nephron
filtration, reabsorption and secretion
what are the three subsections of blood volume regulation
Glomerular filtration, tubular reabsorption, tubular secretion
explain glomerular filtration in relation to blood volume regulation
Glomerular blood pressure causes water & small molecules to be filtered from glomerulus to Bowman’s capsule - only 20% is filtered out
Average glomerular filtration rate?
125ml/min
What influences GMR?
- Renal blood flow & blood pressure
- Filtration coefficient - surface of the glomerular capillaries available for filtration & permeability of capillary-Bowman’s capsule interface
Does GFR fluctuate with BP?
No
Explain tubular reabsorption in terms of blood volume regulation?
Moving substances in the filtrate back into the blood through peritubular capillaries - 180L pass through capillaries - 1.8L excreted - occurs mainly in PCT but some in DCT - active transport, passive adsorption, & transcytosis
What occurs when concentration reaches transport maximum/renal capacity?
Molecules e.g. glucose which would not normally be found in urine are excreted.
Describe the active process of Na reabsorption.
(1) Na+ is the central “ion” involved in tubular reabsorption
(2) water follows Na+ by osmosis
(3) K+, Cl-, HCO3
- follow water by diffusion
(4) Na+ reabsorption uses 6% body energy at rest.
Describe tubular secretion in terms of blood volume regulation.
Movement from extracellular fluid into nephron - K & H secreted to maintain homeostasis - metabolites - active process
What influences the excretion rate of a substance?
Filtration rate & if it is reabsorbed or secreted
What hormones are synthesised by kidneys?
renin & erythropoietin
What hormones are important for kidney function?
ADH & aldosterone
What is aldosterone?
Regulate Na & K levels - increase water retention - increases blood volume & blood pressure
What is ADH?
Increase water absorption in collecting ducts - affects tissue permeability - homeostasis
What is micturition?
Bladder - hollow organ - smooth muscle - 600ml - stores urine - at 250ml - stretch receptors & sensory neurons -signal to spinal cord - urinary bladder contracts, sphincter opens
