Urinary System Flashcards
Functions of the Urinary System
- Removal of waste products
- Assist liver to detoxify poisons
- Regulating blood volume and pressure
- Regulating plasma concentration of Na+, K+, Cl-
- Helping to stabilise blood pH
- Conservation of valuable nutrients
Kidneys location
location: abdominal cavity Left kidney is superior to right. They are surrounded by fat and surface is capped by the adrenal gland.
Ureters
- Paired: transports urine towards the urinary bladder
- Exits the kidney at the renal hilum
- Approx. 30cm long
- Contains smooth muscle for peristalsis
- Lined with transitional epithelium
Urinary Bladder:
- Muscular: smooth muscle – detrusor muscle
- Collects and stores urine for excretion
- Highly distensible
- Lined by transitional epithelium
- Stretch receptors contained within the walls: micturition reflex
discharge of urine involves muscle involuntary and voluntary muscle contractions
stretch receptors trigger reflex
Urethra:
- Transports urine from the bladder for external excretion
- Significant anatomical difference between males and females
- Begins at and form the base of the trigone within the urinary bladder
- Transitional epithelium -> non-keratinised stratified squamous epithelium
Male Urethra:
5 times loner & divided into three segments. The urethra is a common duct for the urinary and reproductive systems in males
Female Urethra:
shorter and only one short tube. The urinary and reproductive systems are completely separate in females.
Nephron Function:
- filtering blood
- reabsorbing useful material from blood filtrate
- secretion of wastes into the urine
Blood vessels of the nephron:
- Deliver blood to nephron so it can be filtered
- Facilitate exchange of substances
Two main parts of nephron:
- Renal Corpuscle
- Renal Tubule
Renal Corpuscle consist of:
- Glomerulus (a tuft of fenestrated capillaries) which form a high-pressure capillary bed
- The double layered glomerular (Bowman’s) capsule which wraps around t he capillaries
- Visceral layer composed of podocytes
Renal Tubule consists of:
filtrate is processes and modified into urine. consists of:
- Proximal Covoluted tube (PCT)
- Loop of Henle
- Distal Convoluted tubule (DCT)
- Collecting Duct
Steps in urine formation:
- Glomerular filtration: in the glomerulus blood plasma and dissolved substances get filtered into the glomerular capsule
- Tubular Reabsorption: along the renal tubule and collecting duct, water, ions, and other substance get reabsorbed from the renal tubule lumen into the peritubular capillaries and ultimately into the blood
- Tubular Secretion: along the renal tubule and collecting duct, substances such as wastes, drugs, and excess ions get secreted from the peritubular capillaries into the renal tubule. These substances ultimately make their way into the urine
regulation of water output:
- urine volume & concentration regulated by ADH
- acts on collecting ducts
- Water re-absorption in collecting ducts is proportional to ADH release
- Decreased = dilute urine and decreased volume of body fluids
- Increased = concentration urine
Aldosterone Regulation of Sodium & Potassium
aldosterone -> active re-absorption of Na+ & secretion of K+
Renal Tubule - Proximal Convoluted Tubule
- Directly attached to renal corpuscle
- Lined with simple cuboidal epithelium
- Microvilli on apical surface increases surface area
- Much of filtrate is reabsorbed (esp. water, glucose, amino acids, & ions)
- Secretion helps to manage pH and rid the body of toxic and foreign substances
Renal Tubule - Loop of Henle
- Descending and ascending regions
- Works to establish a salt concentration gradient in the medulla to promote recovery of water from filtrate
Descending limb of loop of henle:
- Freely permeable to H2O
- Not permeable to NaCl
- Filtrate becomes increasingly concentrated as H2O leaves by osmosis
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Ascending limb of Loop of Henle
- Impermeable to H2O
- Preamble to NaCl
- Filtrate becomes increasingly dilute as salt is reabsorbed
Renal Tubule - Distal Convoluted Tubule (DCT)
- Functions more in secretion tan reabsorption
- Recovery of water and sodium is influenced by hormones
- Aldosterone stimulates sodium reabsorption
- Antidiuretic hormone (ADH) stimulates water reabsorption
Renal Tubule - Collecting Duct:
- Receive filtrate from many nephrons
- Fine tuning of water recovery or disposal
- Water reabsorption through aquaporins regulated by ADH
- Fuse together to deliver urine through renal papillae into minor calyces
