A&P II: Urinary Quiz

Urinary System

• average kidney filters about 180 L/day

• functions of the urinary system

  • regulation of blood ionic composition Na, K, Ca, Cl, & phosphate

  • regulation of blood pH

  • regulation of blood volume/BP

  • regulation of blood glucose levels

  • excretion of wastes and foreign substances

Kidney

• located at about T12-L3

• retroperitoneal - behind peritoneal wall

• right kidney is lower - near liver

  • L kidney is slightly larger than the R kidney; L = larger

• main function

  • renal cortex - form urine

  • renal medulla - collect & excrete urine

The kidney: blood supply

glomerulus - capillary network fitted into the glomerular capsule

afferent arterioles - carry blood to glomerulus

efferent arterioles - carry blood away from glomerulus

• blood comes into renal artery

• the filtered blood exits the kidney via renal vein

about 25% of the blood pumped by the heart/minute goes to the kidneys

The urethra

• internal urethral sphincter - involuntary

• external urethral sphincter - voluntary control

Urination reflex

• voiding = urinating

• mechanoreceptors (stretch receptors) - send signals to the brain

• stretch of detrusor muscle - detrusor muscle contracts —> internal sphincter muscle relaxes —> voluntary control external sphincter muscles to relax

The nephron

• basic unit of kidney function

• processes blood plasma

• forms urine - most abundant nitrogenous waste is urea (not uric acid)

Glomerular filtration

water & small solutes filter out of the blood & into the glomerular capsule; glomerulus in the cortex

• glomerular filtration rate (GFR) - rate of movement of fluid out of the glomerulus & into the capsular space

  • proportional to systemic BP

  • ex: if systemic BP decreased, GFR decreased

Bowman’s capsule

a double walled epithelial cup that surrounds the glomerular capillaries

To produce urine, nephrons, and collecting ducts perform three basic processes

• glomerular filtration

• tubular reabsorption - in PCT, main solutes & reabsorbed by body - water, sodium, chloride are reabsorbed

  • passive and active transport

• tubular secretion

Hydrostatic pressure

gradient that drives the filtration of plasma into the nephron

Antidiuretic hormone (ADH)

• secreted by hypothalamus

• stored in pituitary gland - released

• kidneys: reabsorb more water

• regulates water reabsorption in kidneys by promoting reabsorption of water

• decreases urine production

Diuretics are not effective when treating lymphedema. why not?

lymphedema - retention of protein rich fluid; not water

Normal pH range

7.35-7.45

2 major types of control systems that regulate pH

• chemical

  • bicarbonate buffer system

  • phosphate buffer system

  • protein buffers (hemoglobin, plasma protein)

• physiological

  • respiratory system: regulates CO2

  • renal system: controls bicarbonate and hydrogen ion excretion

pH homeostatic mechanism

• buffers

• respirations

• kidney excretion of acids/bases

Cystitis

bladder inflammation

Thirst mechanism

Osmoreceptors - located in the hypothalamus are stimulated by intracellular dehydration caused by increased osmolality (higher concentration of solutes)

Explain Loop Diuretics

• inhibit reabsorption of sodium and chloride ions in the ascending loop of Henle

• Sodium and chloride are blocked from exiting (staying in tubule) - water will go into the tubule, making more urine output

• higher amount of water in the body = increases blood volume = increases BP; diuretic helps with BP, excreting water of out of body

• more solutes = water will want to go to it = less water; more solutes = less water

  • water will go into the tubules to leave the body as urine

• loop diuretics keep solutes in tubule

  —> water will go into tubule toward

  solutes —> causing solutes to leave the tubule to increase urination

• water will go towards the solutes

Describe how a loop diuretic works in the body to reduce plasma volume and lower blood pressure.

Loop diuretic reduces plasma volume and lower blood pressure by inhibiting reabsorption of sodium and chloride. Loop diuretics will keep the solutes in the tubule, which will cause water to go toward the solutes. Solutes will then leave the tubule which will cause increase in urination. 

Describe the relationship between the kidneys and electrolytes

The kidneys assist in maintaining electrolyte balance in the body. Kidneys regulate levels of electrolytes (sodium, potassium, calcium, chloride) through processes of filtration, reabsorption, and secretion. 

Discuss the homeostatic relationships between the kidneys and the pituitary gland

The kidneys and pituitary gland maintain homeostasis through their interaction in regulating body fluids, blood pressure,and overall fluid balance. This relationship primarily involves ADH, which is produced by the hypothalamus and stored and released by the pituitary gland

Hemodialysis vs. Peritoneal Dialysis

Hemodialysis -

• Frequency: 3x/week

• Access: port or an AVF (arteriovenous fistula)

• Setting: dialysis clinic

Peritoneal Dialysis -

• Frequency: daily

• Access: through the peritoneum

• Setting: at home

Pituitary gland

• Helps regulate water balance in the body through the release of antidiuretic hormone (ADH), based on signals from the hypothalamus

• dehydrated —> hypothalamus (regulation area) —> pituitary gland (release ADH)

• causes increase water reabsorption = increase water in tissue/blood volume = increased BP

• Too much water (edema) - hypothalamus —> pituitary gland to decrease ADH = decrease water reabsorption —> water in tissue/blood volume = decrease BP