Ch. 26 Urinary Sys. (2) The Nephrons

Glomerular capsule aka Bowman's capsule

A double-walled epithelial cap that surrounds the glomerular capilarries; Consists of visceral & parietal layers

Collecting duct

Next filtrate emptying site after the DCT and that converge & empty into papillary ducts

glomerular filtration rate

the process of pressurized filtration of blood by the glomerulus, per unit of time.

Juxtamedullary nephrons

-15-20% of nephrons, -Renal corpuscles lie deep in the cortex, close to the medulla, they have long LOH's that extend into the deepest region of the medulla, -Ascending LOH consists of both thick & thin segments -Receives their blood supply from vasa recta that arise from peritubular capillaries before becoming peritubular venular.

Cortical nephrons

-80-85% of nephrons in kidneys, -renal corpuscles are located in the outer portion on the cortex, with short LOH's that penetrate only a small way into the medulla, -Ascending LOH limbs consist of only a thick segment, -receives their blood supply from peritubular capillaries.

juxtaglomerular apparatus

A collection of cells (macula densa & juxtaglomerular cells) responsible for the hormonal regulation of the body's blood pressure, the kidneys blood flow, & the glomerular filtration rate.

Proximal convoluted tubule (PCT)

A section of the renal tubule located in the kidney's cortex that is responsible for the reabsorption of the majority of the ultrafiltrate; Simple cuboidal epithelial tissue with microvilli

Glomerulus aka glomerular capillaries

Afferent arteriole that divides into a tangled, ball-shaped capillary network

Afferent arteriole

Branch of the interlobal artery that is carrying blood towards the renal corpuscle.

Descending limb of LOH

Composed of a simple squamous epithelium; Dips into renal medulla then ends at the haripin u-turn. Permeable to water

Efferent arteriole

Glomerular capillaries that reunite and carry blood that won't be filtered, away from the renal corpuscle.

Visceral layer of Bowman's capsule

Made up of podocytes that have pedicle that wrap around the single layer of endothelial cells of the glomerular capillaries & form the inner wall of the capsule.

Podocytes

Modified simple squamous epithelial cells with pedicles that wrap around the glomerular capillaries.

Thick ascending limb of LoH

NOT permeable to water only ions. Simple cuboidal to columnar epithelial tissue

Thin ascending limb of LOH

NOT permeable to water, only ions. Composed of simple squamous epithelium; begins in the medulla at the second part of the hair-pin u-turn and ends at DCT. Some nephrons have these in both thick and thin.

Renal tube

Path of filtered fluid after passing through the glomerular capsule; divided into three main sections: The Proximal convoluted tubule, The Loop of Henle, The distal convoluted tubule.

Fenestrations

Pores formed from the visceral & parietal layers in the renal corpuscle that act as a filtration (dialysis) membrane.

Loop of Henle (LOH)

Simple Squamous epithelial tissue made up of: Thick & thin descending limbs, Thick & thin ascending limbs A long duct mainly located in the kidney's medulla that creates a concentrated gradient, called a countercurrent exchange system, which allows for the reabsorption of water.

Nephron

The smallest functional unit of the kidney; ~1 million/kidney; enable the kidneys to create a concentration in the renal medulla & to excrete very dilute or very concentrated urine. Consists of renal corpuscle & renal tubule. Collects filtrate that will ultimately become urine.

Bowman's (glomerular) space

The space between the two layers of the glomerular capsule, aka the lumen of the urinary tube, that is filled with filtered fluid from the glomerular capillaries.

parietal layer of Bowman's capsule

a simple squamous epithelium & forms the outer wall of the capsule.

Renin

an enzyme that helps to increase the body's BP

Types of nephrons

based on the length of the LOH & thin segments of the ascending limbs: Cortical & juxtamedullary

Macula densa

columnar tube cells in the region of the ascending LOH that are crowded together that come into contact with the juxtaglomerular cells of the afferent arteriole; cells that monitor changes in sodium concentration.

Papillary ducts

converging of several collecting ducts that drain into the minor calyces, major calyces, renal pelvis, and ureters.

Pedicles

foot-like projections of podocytes that wrap aroudn the single layer of endothelial cells of the glomerular capillaries & form the inner wall of the capsule.

Juxtaglomerular cells

modified smooth muscle fibers on the afferent arteriole that run alongside the macula densa; Secrete renin.

Distal convoluted tubule (DCT)

simple cuboidal without microvilli & last part consists of simple cuboidal with principal cells that contain receptors for ADH & intercalated cells that are involved in blood pH homeostasis. A duct involved in regulatin the urine's pH, water, & electrolyte balance as well as the channeling of urine out of the kidneys.

Renal corpuscle

structure made up of two subunits: Glomerular capillaries & glomerular capsule