Essel Lecture 1

kidneys

2x, located retroperitoneally in upper dorsal region of the abdominal cavity, responsible for filtering blood and producing urine.

Ureter

tube going from each kidney to the urinary bladder.

Bladder

stores urine

urine

final fluid removed

urethra

tube that conveys urine from the bladder to the outside of the body.

kidney secrets

erythropoietin (RBC production), Renin (regulates blood pressure), Activation of vitamin D to Calcitriol, Gluconeogenesis

Anatomy of kidney

Outer cortex

Inner medulla, containing nephrons that filter blood and produce urine.

Nephrons

functional unit of the kidney.

Makes urine —> minor calyx —→major calyx—→ renal pelvis —→ ureter —→ bladder and urethra.

Blood supply to kidney

Blood enters via renal artery —→ inter lobar—→ inter lobular—→ afferent arteriole——> glomerulus —→ efferent arteriole —→ peritubular capillaries and vasa recta.

Afferent Arterioles

blood to glomerulus

Efferent arterioles

Drains blood from glomerulus

Glomerular Capillaries

high pressure—> filtration

Peritubular capillaries

Low pressure—→ reabsorption and secretion

Glomerulus + Bowman’s capsule

collection point (collects glomerulus filtration)

Proximal tubule

bulk reabsorption of filtered solutes and water

Loop of Henle

a section of the nephron involved in the concentration of urine by reabsorbing water and sodium ions. Establish osmotic gradient

Distal tubule

final site for reabsorption of sodium and water, involved in potassium secretion and acid-base balance. Fine adjustments

Collecting ducts

a series of tubules that connect the distal tubule to the renal pelvis, playing a key role in water reabsorption and electrolyte balance, ultimately influencing urine concentration.

Cortical Nephrons

Short loops of henle

Glomerulus in outer cortex

Juxtamedullary nephron

Long loops of Henle,

glomerulus located near the renal medulla, essential for concentrating urine.

Glomerular filtration

is the process by which blood is filtered in the glomeruli of the kidneys, allowing water and small solutes to pass into the renal tubule while retaining larger molecules and cells in the bloodstream. Restricted by size and driven by pressure gradient.

Favoring filtration

Pushes out

requires high hydrostatic pressure in the glomeruli and a large surface area for filtration to occur effectively. (most important)

Opposing filtration

Pulls in

Resists the movement of fluid into the tubule, which is influenced by factors such as osmotic pressure and the hydrostatic pressure within the Bowman's capsule.

Glomerular hydrostatic pressure

is the pressure exerted by blood within the glomeruli that promotes the filtration of fluid and solutes into the renal tubule, opposing the effects of osmotic pressure.

control points are afferent and efferent atrioles

Plasma Oncotic Pressure

is the osmotic pressure exerted by proteins in the plasma, which pulls water back into the circulatory system, opposing filtration in the kidneys by pulling water back in. This pressure is primarily influenced by albumin and other plasma proteins.

Low plasma protein = High filtration (gfr)

Capsule hydrostatic pressure

is the pressure exerted by fluid in the Bowman's capsule that opposes glomerular filtration, countering hydrostatic pressure from blood in the glomeruli.

High with urinary tract obstruction and low with GFR

Net filtration Pressure (NFP)

is the overall pressure determining the rate of filtration in the kidneys, calculated as the difference between glomerular hydrostatic pressure and the sum of capsule hydrostatic and plasma oncotic pressures.

Favors and drives filtration

Glomerular Filtration Rate (GFR)

volume of plasma being filtered into Bowman’s capsule per unit time

Fenestrated capillary endothelium

Barrier of GFR that blocks cell and large molecules while allowing water and small solutes to pass freely.

Basement membrane

Barrier of GFR that allows passage of only negatively charged molecules and retains larger, positively charged molecules.

Podocytes

Foot process

Barriers of GFR

Negatively charged and prevents albumin from going through

Albumin appears in urine = Proteinurea, damage to glomerulus and damage to filtration

Inulin

used to measure kidney function and GFR, as it is freely filtered at the glomerulus and not secreted or reabsorbed.

Excretion > filtration

substances filtered and secreted more than what is reabsored

Excretion < Filtration

more reabsorbed than secreted

Excretion = Filtration

substances filtered and reabsorbed equal to those secreted.

Para-Aminohippurate (PAH)

a substance used to measure renal plasma flow that is almost completely cleared from the blood by the kidneys.

Autoregulation

a mechanism by which the kidneys maintain a constant rate of blood flow and glomerular filtration despite changes in blood pressure.

High Blood pressure

Causes Afferent constrict and lowers GFR

Low Blood Pressure

causes afferent dilation and increases GFR

Macula Densa Cells

are specialized cells in the distal convoluted tubule that sense changes in sodium concentration and regulate renal blood flow and glomerular filtration rate.

Too much Na+ it tells the glomerulus to constrict the afferent arterioles and decrease GFR.

Efferent Constrict

High GFR

Efferent Dilates

Low GFR