Human Anatomy: Kidneys Overview

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Questions and Answers

What role do juxtamedullary nephrons primarily play in the kidneys?

They are responsible for producing dilute urine.

They create conditions for producing concentrated urine. (correct)

They eliminate excess ions and maintain electrolytic balance.

They filter blood without reabsorbing any substances.

What is the primary function of the distal segments of the nephron?

They reabsorb useful metabolic substrates and secrete waste. (correct)

They exclusively excrete excess water.

They filter blood plasma without reabsorption.

They only manage ion concentration in the blood.

How does the filtration process in the kidneys primarily operate?

By restricting only large molecules from entering the filtrate.

By allowing solutes to pass through a barrier based solely on their solute size. (correct)

By using active transport to move ions against concentration gradients.

By concentrating urine before it reaches the renal pelvis.

What percentage of water is typically reabsorbed by the distal segments of the nephron?

Around 80% Signup and view all the answers

What characteristic distinguishes juxtamedullary nephrons from other nephron types?

They have longer loops of Henle that extend deep into the medulla. Signup and view all the answers

What is the primary function of juxtaglomerular cells in the kidney?

Secreting renin Signup and view all the answers

Where are extraglomerular mesangial cells located?

Between the afferent and efferent arterioles of the glomerulus Signup and view all the answers

Which part of the nephron connects to the collecting system?

Distal convoluted tubule Signup and view all the answers

What structures comprise the collecting system of the kidneys?

Connecting tubules, collecting ducts, and papillary ducts Signup and view all the answers

Which nephrons play a critical role in urine concentration?

Juxtamedullary nephrons Signup and view all the answers

How do juxtaglomerular cells respond to low blood pressure?

Secrete renin Signup and view all the answers

What is the main purpose of the feedback control between mesangial cells and juxtaglomerular cells?

To stabilize glomerular filtration rate Signup and view all the answers

Which of the following processes occurs in the collecting system?

Reabsorption of water Signup and view all the answers

What do juxtamedullary nephrons primarily contribute to in the kidneys?

Reabsorption and secretion Signup and view all the answers

Where are juxtamedullary nephrons primarily located within the kidney?

Closer to the medulla Signup and view all the answers

What is a distinguishing feature of juxtamedullary nephrons compared to cortical nephrons?

Longer nephron loops extending deep into renal pyramids Signup and view all the answers

Which type of nephron performs most of the reabsorptive and secretory functions in the kidneys?

Cortical nephrons Signup and view all the answers

Which structures receive blood after it drains from the capillaries?

Interlobular veins Signup and view all the answers

What percentage of nephrons are classified as juxtamedullary nephrons?

15 percent Signup and view all the answers

What is the primary function of capillaries in the kidney nephron?

Blood drainage to venules Signup and view all the answers

Which of the following statements about nephron loops is correct?

Juxtamedullary nephrons have longer loops that extend deep into renal pyramids. Signup and view all the answers

Study Notes

26.1 The Kidneys

The kidneys are retroperitoneal, located on the posterior abdominal wall.
Adrenal glands sit on the superior surface of the kidneys.
Three layers of connective tissue stabilize each kidney.
Kidneys are positioned lateral to the vertebral column, between the last thoracic and third lumbar vertebrae.
The right kidney sits slightly lower than the left kidney due to the liver's presence on the right side of the abdominal cavity.

Kidney Structure and Support

The fibrous capsule is the outermost layer, providing protection and maintaining kidney shape.
The perinephric fat (adipose tissue) surrounds the fibrous capsule.
The renal fascia anchors the kidney to surrounding structures and the posterior body wall.
Pararenal fat pads separate the posterior and lateral portions of the renal fascia from the body wall.

Superficial Anatomy of the Kidney

The hilum is the entry point for the renal artery, renal nerves, and exit point for the renal vein and ureter.
A typical adult kidney is ~10cm long, ~5.5cm wide, and ~3cm thick.
A single kidney weighs approximately 150g.
Each kidney has a bean-shaped form with an indentation on its medial surface called the hilum.

Sectional Anatomy of the Kidney

The kidney interior contains renal cortex, renal medulla, and renal sinus.
The renal cortex is a granular, reddish-brown region, deep to the renal capsule
The renal medulla is deep to the cortex and has renal pyramids.
Renal papillae, located at the tips of the pyramids, project into the renal sinus.
Renal columns are bands of cortical tissue that extend into the medulla, separating adjacent renal pyramids.
A kidney lobe comprises a renal pyramid, the overlying cortex area, and adjacent renal columns.
Urine is produced within kidney lobes. The urine then flows into minor calyces which merge to form major calyces, then the renal pelvis. Urine production occurs in the nephrons. These are microscopic tubular structures.
Approximately 1.25 million nephrons in each kidney.
The combined length of all nephrons is about 145km (90 miles).

The Blood Supply to the Kidneys

Kidneys receive 20-25% of the cardiac output.
Blood flows to the kidneys via a renal artery, branching into segmental, interlobar, arcuate, and cortical radiate arteries.
Blood is delivered to individual nephrons via afferent arterioles.
Blood leaves the nephrons via efferent arterioles.
Blood is drained from the kidneys via interlobar veins and renal veins.

Innervation of the Kidneys

Both branches of the autonomic nervous system innervate the kidneys.
Mostly sympathetic post-ganglionic fibers from the celiac and inferior mesenteric ganglia.
Sympathetic innervation adjusts urine formation rates and composition of urine, by stimulating the release of renin.

Histology of Kidney

The nephron is the kidney's basic structural and functional unit.
Tubular segments are named based on location, thickness, and shape (e.g., proximal convoluted tubule, nephron loop).

The Renal Corpuscle

The renal corpuscle consists of glomerular capsule and its glomerulus capillary network.
Filtrate is produced in the renal corpuscle as blood pressure forces fluid and solutes out of glomerular capillaries.
The filtration involves 5 barriers: endothelial layer, glycocalyx, basement membrane, glomerular epithelium, podocyte processes.
Filtrate composition is similar to plasma, but lacks blood proteins.

The Proximal Convoluted Tubule

First part of the renal tubule
Re-absorbs organic nutrients, ions, and plasma proteins from the filtrate.
Re-absorbs 60% of sodium, chloride ions and water.
Osmotic forces move water into surrounding peritubular fluid.

The Nephron Loop

The nephron loop, or Loop of Henle, is a hairpin-shaped structure that concentrates the solutes in the renal medulla.
The descending limb and ascending limb are lined with simple squamous epithelium.
Reabsorbs an additional 25% of water from the tubular fluid and significant amount of sodium and chloride ions.

The Distal Convoluted Tubule

The distal convoluted tubule (DCT) is surrounded by capillaries called peritubular capillaries
An important area for secretion of substances (i.e., ions, acids) and reabsorption of substances (i.e., sodium and calcium).
Regulation by the circulating levels of aldosterone

The Juxtaglomerular Complex

A specialized structure that regulates blood pressure and filtration rate.
Composed of macula densa cells, juxtaglomerular cells, and extraglomerular mesangial cells.
Macula densa cells monitor sodium concentration in tubular fluid
Juxtaglomerular cells secrete renin when blood volume or blood pressure falls.

The Collecting System

The collecting system is a series of tubes that carry tubular fluid away from the nephron.
Connecting, collecting, and papillary ducts progressively transport filtrate to the renal pelvis.
Antidiuretic hormone (ADH) regulates the permeability of the collecting ducts to water.
High ADH levels promote reabsorption of water, producing concentrated urine.

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Description

This quiz covers the basic anatomy and structural support of the kidneys. It includes details about their location, surrounding structures, and specific features like the fibrous capsule and fat layers. Test your knowledge about the kidneys and their functions.