Urinary System Flashcards
Describe the structure of the kidney
Located retroperitoneally in perirenal capsul
What are the functions of the urinary system
Dispose of metabolic waste and excess substances through formation of urine + filters the blood: gets rid of nitrogenous waste ammonia etc. salts glucose vitamins.
Regulate fluid electrolyte balance. Regulate acid-base balance in blood. Produce hormone erythropoietin
What are the three regions of the kidney
Cortex, medulla and pelvis
What is the cortex of the kidney
Outer region. Lightly colored and granular
Describe the medulla
Darker, reddish brown. Contains cone shaped renal pyramids that are striated. Composed of parallel bundles of urine collecting tubules. The renal pyramid and surrounding cortical tissue constitutes a lobe
Describe the pelvis of the kidney
Flat, funnel shaped tube continuous with ureter and exits out the hilium
What are the major calyces
Large branches of the renal pelvis that are subdivided into several minor calyces. Collect urine draining from papilla of each renal pyramid. Empty urine into the renal pelvis
How does the urine flow through the pelvis and ureters to the bladder
By peristalsis
What are ureters
Tubes connecting the renal pelvis to the bladder. Ureters enter bladder at an oblique angle and when bladder is full shape changes and pinches off ureters to prevent backflow of urine
What are the three tissue layers that the wall of the ureter is composed of
It are mucosal layer is transitional epithelium. Middle layer is smooth muscle. Outer layer is fibrous
Describe the urinary bladder
Stores urine until a limitation. Stretching of wall makes it thinner and more susceptible to rupture. Stretch receptors trigger contractions. Involuntary sphincter control is urine flow into urethra.
Describe the urethra
Tube connecting bladder to outside of body. Typically longer in males but not true and cats.
What does the urethra carry in females
Urine
What does the urethra carry in males
Urine and semen
Describe kidney filtration
Kidneys receive one fourth of aortas blood at any given time. All of body’s blood is filtered every five minutes. 25% of blood plasma enters the nephron as filtrate. All but one percent of filtrate is reabsorbed back into the blood by capillories surrounding the nephron that are called peritubular capillaries. Remaining filtrate enters calyces as urine.
Describe blood flow to and from kidneys
Aorta ➡️ renal artery➡️afferent arteriole ➡️glomerulus ➡️peritubular capillaries ➡️renal vein ➡️inferior vena cava
How is the kidney capillary bed and the regular capillary bed different
This capillary bed is different because it is forced movement not by concentration gradient.
What is the renal corpuscle
The glomerulus and the Bowmans capsule
What is a nephron
Structural and functional renal unit. Forms urine
What does the nephron consist of
Glomerulus
Bowmans capsule
Renal tubule
Describe the glomerulus
Capillary bed. Blood enters under high-pressure. Endothelium is fenestrated. Filtration of blood is selective only by size. Filtrate enters the renal tubule after the glomerulus
What can pass through the glomerulus
Plasma + dissolved solutes
What shouldn’t pass through the glomerulus
Proteins, cells. Too large to be re absorbed and will Be thus present in urine
Describe the Bowmans capsule
Surrounds glomerulus and is continuous with the renal tubule. Odor parietal layer is simple squamous epithelium. Inner visceral layer consists of podocytes that cling to basement membrane. Filtrate passes through fenestrations between the feet in the capsule
Where are the pct and dct located
The cortex
Where are the loop of henle and the collecting ducts
Medulla
Describe the proximal convoluted tubule
Simple cuboidal epithelium with microvilli brush border. Reabsorbs water and solids from filtrate and returns to blood via peritubular capillaries. Secrete substances into filtrate.
Describe the loop of Henle
Loop of the renal tubule that dips into the medulla.
What are the two portions of the loop of Henle
The descending limb and the ascending limb
Describe the descending limb of the loop of Henle
Proximal part has cells similar to proximal convoluted tubule then becomes narrow and has simple squamous cells freely permeable to water
Describe the ascending limb of the loop of henle
Tube widens again epithelium is cuboidal and columnar and inpermeable to water
Describe the distal convoluted tubule
Cuboidal cells without microvilli. Not as twisted as proximal convoluted tubule. Functions more in secretion than reabsorption. Empty into collecting ducts.
Describe the collecting ducts
Receive filtrate from numerous distal convoluted tubule’s. Deliver filtrate to renal pelvis. Composed of two cuboidal cell types. Principal cells maintain water and potassium balance and intercalcated cells maintain acid-base balance and have microvilli
Describe the glomerulus capillary bed
Fed by afferent arteriole, drained by efferent arteriole. Produces filtrate
Describe the peritubular capillaries
Site of reabsorption and secretes. Site of gas exchange. Merge to form renal vein
What are the three major processes in urine formation and adjustment of blood composition
Glomerulus filtration
Tubular reabsorption
Tubular secretion
Describe filtration
Occurs at glomerulus, size selective only
Describe reabsorption
Tubule➡️peritubular capillaries. Good stuff lost at glomerulus is returned to blood unless in excess. All of glucose and amino acids should be reabsorbed
Describe secretion
️peritubular capillaries ➡️ tubules. Bad stuff not filtered in glomerulus transported to tubule for excretion
Where should reabsorbed and secreted substances also pass through
Institial space between vessels and nephron. Transport may be passive (diffusion) or active (ATP). Osmotic gradient in medulla affects transport