Structure and function
Name 4 functions of the urinary system.
1. maintenance of fluid and electrolyte balance (osmolarity)
2. regulation of pH
3. helps regulate blood volume and pressure
4. excretion of metabolic wastes
5. production of hormones erythropoietin and renin
6. assist liver in detoxification
7. glucogenesis
How is GFR affected by dilation of afferent arterioles?
How is GFR affected by dilation of efferent arterioles?
Dilation of afferent arterioles increases GFR.
Dilation of efferent arterioles decreases GFR.
Microvilli
Is tubular secretion selective or non-selective?
Selective
What is the role of ANP? Where is it released from and what does it do?
Order fluid flow through the tubular components of the nephron.
(1) Distal tubule, (2) Proximal tubule, (3) Juxtaglomerular apparatus, (4) Collecting duct, (5) Bowman's capsule, (6) Loop of Henle
5, 2, 6, 3, 1, 4
What features of the glomerulus allow filtration rate to be higher than in capillaries elsewhere in the body?
- fenestrations
- podocytes
What forces drive the reabsorption of water into the peritubular capillaries?
Osmosis
Why is it important to secrete H+ ions in the kidneys? What would increasing the secretion of H+ do to the blood?
Regulates acid-base balance of the blood. Secreting H+ increases the pH of the blood (more alkaline).
Where is renin released from and what does it do?
Renin is released from juxtaglomerular cells in the kidney and activates the conversion of angiotensinogen to angiotensin I.
Order the blood flow through the vessels of the kidney.
(1) Vein, (2) Afferent arteriole, (3) Efferent arteriole, (4) Artery, (5) Glomerulus, (6) Peritubular capillaries
4, 2, 5, 3, 6, 1
Why is it important that proteins cannot be filtered out across the glomerular membrane?
What is the role of the loop of Henle? What is reabsorbed in the ascending and descending limbs?
What hormone controls the amount of K+ secreted? In what part of the nephron is K+ secreted?
What is the role of vitamin D in regulating ion concentration in the blood? What is the mechanism of action?
Juxtamedullary nephrons establish a vertical osmotic gradient in the medulla. Their loops of henle are long, running deep into the medulla.
Cortical nephrons make up the majority and are responsible for concentrating urine. They are located more superficially in the cortex and their loops of henle only slightly dip into the medulla.
Where in the nephron does unregulated reabsorption occur? What substances are reabsorbed here?
Where in the nephron does regulated reabsorption occur? What substances are reabsorbed here?
Distal tubule. Water and electrolytes.
What is the formula for volume of urine secreted using glomerular filtration, tubular reabsorption, and tubular secretion.
Amount excreted = amount filtered + amount secreted – amount reabsorbed
Angiotensin I is converted to angiotensin II in the lungs by ACE. What systematic effects does angiotensin II have and what are its mechanisms of action?
Angiotensin II stimulates the secretion of aldosterone from the adrenal cortex which causes increased Na and decreased K reabsorption. The increased blood osmolarity stimulates the secretion of ADH from the PPG. It also stimulates thirst receptors in the hypothalamus and vasoconstriction of systemic arterioles and veins. All of these result in increasing BP
What are the three processes in urine formation that involve fluid and solute movement into and out of the blood stream to concentrate the urine? For each of these, where are fluid and solutes moving from and to?
Glomerular filtration: protein-free plasma from glomerulus to Bowman’s capsule
Tubular reabsorption: from tubular lumen into peritubular capillaries
Tubular secretion: from peritubular capillaries into the tubular lumen
Describe the intrinsic mechanisms of myogenic response and tubuloglomerular feedback. How do they influence GFR?
In tubuloglomerular feedback, macula densa cells detect stretching of the tubules caused by increased GFR and secrete paracrine chemical messengers to stimulate constriction of afferent arterioles.
How does glucose cross the apical membrane of tubular epithelial cells?
How does glucose cross the basolateral membrane of tubular epithelial cells?
How does glucose cross the peritubular capillary endothelium?
Where do ADH and atrial natriuretic peptide hormone come from? Where do they work in a nephron? What ions do they control secretion of?
ADH is released from the posterior pituitary gland and atrial natriuretic peptide hormone is released from the heart. They both work on the distal and collecting tubules of a nephron but have opposite effects. ADH decreases the secretion of Na and atrial natriuretic peptide hormone increases the secretion of Na.
Trace the path of ADH from where it is secreted to where it binds and how it affects its target cells.