Renal Exam 5 Flashcards
Anatomy of the Kidney: Functional portion, functional unit, nephron
Functional portion: Parenchyma
Functional unit: nephron
Nephron: renal corpuscle and renal tubules
Kidneys: Maintenance of homeostasis
Blood ionic composition: Na, K, Ca, Cl, HPO4
Blood pH: Excretion of H+
Blood Volume: Conservation or elimination of water
Blood Osmolarity: Regulating loss of water and solutes in urine
Kidneys: Removal of substances from blood
Metabolic waste and chemicals: urea (aa), creatinine (creatine phosphate in muscle), bilirubin (hemoglobin)
Drugs and metabolites
Kidneys: Regulation of processes
Hormone production: Calcitriol (activate Vit D) and Erythropoietin
Blood Pressure: renin release
Blood Glucose Levels: Gluconeogenesis (Gln)
Functional portion of kidneys contains two distinct regions
Renal cortex (superficial area)
Renal medulla (inner portion)
they constitute the parenchyma or functional portion
Nephrons: location and used for
Located in both cortex and medulla
Used for filtration of blood & reabsorption & secretion of materials
Nephrons: parts and functional units
Parts: renal corpuscle and renal tubule
Functional Units because they: form urine, remove waste from blood, regulate water and electrolyte concentrations
Nephron: Renal Corpuscle
Renal corpuscle is the filtration unit
Composed of: glomerulus, glomerular or Bowman’s capsule
Renal Tubule sections
1: Proximal Convoluted tubule
2: Loop of Henle
3: Distal Convoluted Tubule
Collecting Tubule often is not considered as part of the nephron
Types of Nephrons
Two types based on anatomical location
-Cortical nephrons
-Juxtamedullary nephrons
Cortical Nephrons
Corpuscles located closer to surface of the kidney (renal capsule)
SHORT nephron loops: extend only to outer region of renal medulla
80% of nephrons (near top of cortex)
Juxtamedullary Nephrons
Corpuscles in the cortex but close to renal medulla
Nephron loops extend deep into the renal medulla
20% of nephrons
Important for regulating water
Arterial and Venous blood supply to the kidney
Arterial flow brings blood into the kidney:
-Renal Artery
-Transports O2 blood from heart and aorta to kidney for filtration
Venous flow takes blood out of the kidneys:
-Renal Vein
-Transports filtered and deoxygenated blood from the kidney to the posterior vena cava and then the heart
Arterial blood supply to the kidneys
-Kidney receives blood via renal artery (1)
-Renal artery divides into segmental arteries (2)
-Segmental arteries branch (3)
— enter the parenchyma and pass through renal columns as interlobar arteries
Blood flow from renal column to the renal cortex as follows in the kidney:
-Interlobar arteries arch at the base of the pyramids (between medulla and cortex) forming arcuate arteries
-Arcuate arteries divide producing interlobular arteries
-Interlobular arteries enter the renal cortex and branch off to form afferent arterioles, which supply the nephron
Blood supply to the Glomerulus: Efferent arteriole, afferent arteriole
Afferent arteriole:
-Transports arterial blood to the glomerulus for filtration
-Divides into glomerular capillaries
-Has larger diameter than efferent arteriole
-Passes blood to the efferent arteriole
Efferent arteriole:
-It carries blood out of the glomerulus
-efferent arteriole give rise to capillaries that surround renal tubule
Blood Supply of Renal Tubule of Cortical Nephrons
-Peritubular capillaries originate from efferent arteriole
-Capillaries are low-pressure, porous and adapted for absorption
-They surround the tubules mainly in the renal cortex and the short loop of Henley in the medulla
-They empty into interlobular veins
Blood Supply of Renal Tubule in Juxtamedullary Nephrons
Efferent arteriole originates the vasa recta capillaries
Vasa recta is deep down into the medulla
-parallels the Loop of Henle in juxtamedullary nephrons
-they carry blood at a slow rate
-helps to concentrate the filtrate
Renal Venous System
-Takes blood out of the kidneys
-From the nephron blood enters the interlobular veins
-Blood drains through the arcuate veins
-From arcuate veins blood enters the interlobar veins between the pyramids
-Blood leaves the kidney through a single renal vein
Renal blood supply pathway:
Renal Artery
Interlobar artery
Arcuate artery
Interlobular artery
Afferent arteriole
Glomerulus
Efferent arteriole
Interlobular vein
Arcuate vein
Interlobar vein
Renal vein
Processes of Urine Formation: Reabsorption, Filtration, Secretion
-selective process
-right amount of substances, H2O, electrolytes, glucose enter blood
-waste products and substances in excess are not reabsorbed
Processes of Urine Formation: Filtration
-Water and solutes from blood
-Based on size
Processes of Urine Formation: Secretion
-Removes substances that must be eliminated from the blood
-Lower plasma concentration of undesirable materials
Glomerular Filtration: occurs where, what moves accross capillaries, where does it move
Occurs: in the renal corpuscle
Move freely across glomerular capillaries: Inorganic ions, low molecular weight solutes, and water
From the glomerular capsule, the filtrate moves into the renal tubule
Glomerular Filtration: what are the filtered substances
Commonly filtered substances:
Ions such as Na, K, Cl, HCO3
Natural organic such as glucose and urea
Amino Acids, vitamins, and small proteins are also filtered
Components of Renal Corpuscle: Glomerulus and Glomerular (Bowman’s) capsule
Glomerulus:
site for blood filtration
semi-permeable capillary network - caused by afferent capillaries
filtrate -> product of glomerulus
Glomerular (Bowman’s) capsule:
Epithelial cup or sac surrounding capillaries
Transfer filtrate from glomerulus to Proximal Convoluted Tubule (PCT)
Histology of Bownman’s Capsule: Parietal Layer and Visceral Layer
Parietal Layer:
Outer wall of glomerular capsule
Squamous epithelial cells
Visceral Layer:
Covers glomerulus
Podocytes -> modified squamous cells, component of glomerular filtration barrier
Components of Podocytes
Primary process -> cell surface extensions from cell body
Secondary -> fingerlike extensions aka pedicels
(hand -> fingers (gaps in fingers that water can seep through)
Filtration Membrane or Barrier of Renal: filtration, barrier
Filtration of water and small solutes
Effective barrier for most plasma proteins, blood cells, and platelets
Filtration Membrane: Components (layers)
Podocytes: (outside)
form filtraition slits
Basement Membrane or Basal Lamina:
glycoprotein matrix
collagen and proteoglycans
located between endothelium and podocytes
Endothelial Cells: (inside)
have fenestrations, leaky
Filtration Process forces
Outside: forces opposing filtration
Inside: (in blood) force favoring filtration
Force Favoring Filtration
Glomerular blood hydrostatic pressure (GBHP)
-Blood pressure in the glomerular capillaries
-Generally is high -> efferent arterioles are smaller than afferent arterioles
Forces Opposing Filtration
Capsular Hydrostatic Pressure (CHP)
-Pressure exerted by fluid already in the capsular space and renal tubules
Blood colloid osmotic pressure (BCOP) -> Due to the presence of proteins in plasma
Net Filtration Pressure (NFP)
Glomerular Blood Hydrostatic Pressure (55 mmHg)
Capsular Hydrostatic Pressure (11 mmHg)
Blood Colloid Osmotic Pressure (30 mmHg)
55mg - 15 mmHg - 30 mmHg = 10 mmHg
*filtration ceases when the glomerular blood pressure is 45 mmHg
Control of Glomerular Filtration Rate
-GFR is the volume of fluid filtered from the glomerulus into Bowman’s space per unit time
-GFR can change, but subject to physiological regulation
-Neuronal and hormonal mechanisms are important to maintain a nearly constant glomerular filtration rate
-Regulation of the afferent and/or efferent arterioles adjust blood flow in and out of the glomerulus changing the net GF pressure
Decreased GFR
-Construction of the afferent arterioles
-Decreases the hydrostatic pressure in glomerular capillaries
(smaller AA in front)
-Dilation of efferent arterioles
-Decreases the hydrostatic pressure in glomerular capillaries
(dilate EA in back)
Increased GFR
-Constriction of the efferent arterioles
-Increase the hydrostatic pressure in glomerular capillaries
(Constrict EA in back)
-Dilation of the afferent arterioles
-Increase the hydrostatic pressure in the glomerular capillaries
(dilate AA in front)