L1: Renal Histology, Function and Circulation Flashcards
Functions of the Kidneys?
Regulation of water and electrolyte balance
Excretion of metabolic waste and bioactive substances
Regulation of arterial blood pressure
Regulation of erythrocyte production
Regulation of Vitamin D production
Gluconeogenesis (glucose synthesis)
What metabolic waste and bioactive substances do the kidneys excrete?
Urea (from protein)
Uric acid (from nucleic acids)
Creatinine (from muscle creatine)
Drugs/Hormones
How do the kidneys regulate arterial pressure?
Regulation of blood volume
Renin production (Renin-Angiotensin-Aldosterone System (RAAS))
Role of Kidneys in regulating erythrocyte production?
Kidney is major site of Erythropoietin (EPO) production (Fibroblasts)
Released fro fibroblast cells when local tissue oxygen levels are reduced
EPO stimulates the bone marrow to increase production of erythrocytes and therefore haemoglobin
How do the kidneys regulate Vitamin D Production?
Active form of Vitamin D (Calcitriol) is made in the kidneys => Promotes calcium and phosphate absorption from the gut
Role of Kidneys in Maintaining blood glucose?
Gluconeogenesis: Synthesis of glucose from non carbohydrate sources during periods of fasting
Predominant type of tissue type in renal capsule is ____________ connective tissue
Surrounded by perinephric fat and then by the ______________, which also encloses the ____________________________
Predominant type of tissue type in renal capsule is fibrous connective tissue
Surrounded by perinephric fat and then by the perinephric (perirenal) fascia, which also enclose the adrenal gland (produces aldosterone)
What penetrates the renal Hilum?
Renal artery
Renal vein
Lymphatics
Renal nerve
Renal pelvis
Three distinct regions of the kidney and their constituents?
Cortex (Location of glomeruli of nephrons)
Medulla (Nephrons’ tubules)
Renal pelvis (major and minor calyces collect urine and empty it into the renal pelvis)
Arteries/Veins located at the boundary of cortex and medulla of kidneys?
Arcuate Arteries/Veins
Arteries/Veins located in the cortex of kidneys?
Interlobular Arteries/ Veins
Path of blood flow in kidneys?
Vascular supply to the two types of Nephrons in Kidneys?
Peritubular Capillaries (Cortical Nephrons)
Vasa Recta Capillaries (Juxtamedullary Nephrons)
Cortical vs. Juxtamedullary Nephrons?
Cortical Nephrons:
- Glomeruli located in the ___________
- Responsible for _______________________
- Supplied by ____________________
Juxtamedullary Nephrons:
- Glomeruli are in the ___________________
- Produce __________________________
- Supplied by ________________________
Cortical Nephrons:
- Glomeruli located in the outer cortex
- Responsible for majority of reabsorption within the kidney (80-85% of nephrons)
- Supplied by Peritubular Capillaries
Juxtamedullary Nephrons:
- Glomeruli are in the inner cortex (near the medulla)- NO Glomeruli in Medulla!!
- Produce concentrated/diluted urine
- Supplied by Vasa Recta Capillaries (Straight Vessels)
Collections of straight tubules form the ________, which run up the centre axis of a renal lobule
Region of cortex between the rays is called ___________
Collections of straight tubules form the medullary rays, which run up the centre axis of a renal lobule
Region of cortex between the rays called the cortical labyrinth
Structures of the Juxtaglomerular Apparatus?
Macula Densa of the Thick Ascending Limb: columnar epithelial cells that act as salt sensors
Extraglomerular Mesangial Cells: specialized smooth muscle cells that regulate blood flow
Granular Cells (Afferent Arteriole): specialized smooth muscle cells that manufacture, store and release RENIN
Columnar epithelial cells of the Juxtaglomerular Apparatus that act as salt sensors?
Macula Densa (Thick Ascending Limb)
Specialized smooth muscle cells of the Juxtaglomerular Apparatus that regulate blood flow?
Extraglomerular Mesangial Cells
Specialized smooth muscle cells of the Juxtaglomerular Apparatus that manufacture, store and release RENIN
Granular cells (Afferent Arteriole)
Thickness of Renal Tubule?
All tubules are a single layer of epithelial cells: permits exchange of fluid/solutes between the tubule and the surrounding interstitial/vasculature
Section of renal tubule composed of simple cuboidal epithelial cells with extended brush borders?
Proximal tubule
Section of renal tubule composed of Squamous (flattened) epithelium
Thin Descending and Ascending Limbs
Section of renal tubule composed of Cuboidal epithelium with invaginated basolateral membranes?
Thick Ascending Limb and the Distal Tubule
Section of Renal Tubule composed of columnar epithelium?
Collecting Duct Cells:
- principal cells (NaCl reabsorption and K+secretion)
- intercalated cells (acid-base balance)
Cell Type of the Renal Collecting duct responsible for NaCl reabsorption and K+ secretion?
Principal Cells
Cell Type of the Renal Collecting duct responsible for Acid-Base balance?
Intercalated Cells
Blood Flow to Kidneys?
Renal blood flow ~950 –1100 ml/min (20% of the cardiac output)
Far in excess of kidneys’ metabolic needs providing kidneys the flexibility to alter blood flow in response to physiological demand
Capillary Beds in the Kidney
Why is hydrostatic pressure at afferent renal arterioles high relative to non-renal vascular beds?
Presence of second set of arterioles after glomerular capillaries -Efferent arterioles offer resistance to the blood flow
Branching of glomerular capillaries leads to increased cross-sectional area and results in only minor drop in pressure
Glomerular capillary hydrostatic pressure (PCAP)?
45mmHg –60mmHg
Why does Π CAP increase along the length of the glomerular capillaries?
- fluid leaving glomerular capillaries
- large proteins not filtered
Purpose of variable pressures along the renal circulation?
Influences filtration and reabsorption
Net Filtration: occurs along the length of glomerular capillaries -afferent end (18mmHg) and efferent end (5mmHg)
Reabsorption: along the length of peritubular capillaries due to further reduction in Capillary hydrostatic pressure in efferent arterioles, whereas oncotic pressure is high (35mmHg)
What is the normal value for net filtration pressure (NFP) at the afferent vs. efferent end of glomerular capillaries?
5 mm HG
NET Outward pressure from afferent to efferent
Where in the Renal Vascular bed does net filtration occur?
Glomerular Capillaries
Where in the Renal Vascular Bed does net Reabsorption occur?
Peritubular Capillaries
