The Kidney Anatomy

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Questions and Answers

What is the main function of the renal corpuscle in the nephron?

Absorption of nutrients

Regulation of blood flow

Filtration of fluid (correct)

Secretion of hormones

Which component of the nephron is responsible for transporting filtered fluid away from the glomerulus?

Afferent arteriole

Collecting duct

Proximal convoluted tubule (correct)

Distal convoluted tubule

Where do the renal tubules connect to the collecting ducts?

In the renal pelvis

In the minor calyx

In the medulla (correct)

In the major calyx

What is a key characteristic of juxtamedullary nephrons compared to cortical nephrons?

They have longer loops of Henle Signup and view all the answers

Which sequence accurately represents the flow of urine from the nephron to the urinary system?

Proximal convoluted tubule → Distal convoluted tubule → Collecting duct → Major calyx → Renal pelvis Signup and view all the answers

What structures are located at the hilus of the kidney?

Renal artery, nerves, renal vein, and ureter Signup and view all the answers

Which layer of tissue surrounds the kidneys and is directly in contact with the outer surface?

Renal capsule Signup and view all the answers

What is the predominant structure found in the inner region of the kidney?

Renal pyramids Signup and view all the answers

What is the average length of an adult kidney?

10 - 12 cm Signup and view all the answers

Which region contains the functional nephrons of the kidney?

Outer cortical region Signup and view all the answers

How many renal pyramids are typically found in the medulla of a kidney?

6 - 18 Signup and view all the answers

What is the primary purpose of the renal fascia?

To anchor kidneys to body structures Signup and view all the answers

Where does urine collect within the kidney before draining to the bladder?

Renal sinus Signup and view all the answers

What is the main function of the trigone in the urinary bladder?

To funnel urine into the urethra upon contraction Signup and view all the answers

Which layer contributes to the detrusor muscle of the bladder?

Both A and B Signup and view all the answers

How long is the male urethra compared to the female urethra?

Longer by 15-17 cm Signup and view all the answers

What type of epithelium is found at the neck of the bladder?

Transitional epithelium Signup and view all the answers

Which muscle group is under voluntary control to facilitate micturition?

External urethral sphincter Signup and view all the answers

What is one of the primary functions of the kidneys?

Excretion of organic waste products Signup and view all the answers

The inner mucosa of the urethra is primarily made of which structure?

Transitional epithelium Signup and view all the answers

What does micturition refer to?

The release of urine from the bladder Signup and view all the answers

Study Notes

The Kidney

The kidneys are bean-shaped organs, located in the retroperitoneal space, above the waist.
An adult kidney measures about 10-12 cm long, 5-7.5 cm wide, and 2.5 cm thick.
The hilum is a medial indentation where blood vessels, nerves, and the ureter enter and exit.
The renal sinus is the internal cavity where urine collects before flowing to the bladder.

### Kidney Tissue Layers

The kidney is enclosed by three layers:
- The renal capsule: a collagen fiber layer covering the kidney's outer surface, continuous with the ureter's outer coat.
- The adipose capsule: a thick layer of fat surrounding the renal capsule.
- The renal fascia: a dense, fibrous layer anchoring the kidney to the posterior body wall and anterior peritoneum.

### Internal Kidney Anatomy

The kidney's internal anatomy includes:
- The cortex: the outer granular and reddish-brown region in contact with the renal capsule.
- The medulla: the inner region consisting of 6-18 renal pyramids.
- Renal pyramids: conical or triangular structures with the base facing the cortex and the tip (renal papillae) projecting into the renal sinus.
- Outer cortical region/juxtamedullary zone: the functional nephrons can originate in the outer cortex (cortical nephrons) or the region close to the medulla (juxtamedullary nephrons).
- Renal columns: bands of cortical tissue separating the renal pyramids.
- Parenchyma: the functional part of the kidney, constituted by the cortex and renal pyramids.

### The Nephron

The nephron is the functional unit of the kidney, responsible for filtration, secretion, and absorption. Each kidney contains approximately 1 million nephrons.
The nephron consists of the following components:
- Renal corpuscle:
  - Where fluid is filtered.
  - Contains the glomerulus (capillary network) enclosed within the glomerular (Bowman's) capsule.
- Renal tubules:
  - Where filtered fluid passes through.
  - Blood enters through the afferent arteriole and exits through the efferent arteriole.
The renal tubule includes:
- Proximal convoluted tubule (PCT).
- Loop of Henle (U-shaped nephron loop) separating the PCT and DCT.
- Distal convoluted tubule (DCT).

Collecting Ducts

Short connecting tubules link the DCTs of multiple nephrons to a single collecting duct.
Collecting ducts descend through the medulla to papillary ducts at the medulla's base.
The fluid then drains into the minor calyx, where four to five minor calyces merge into a major calyx.
Two to three major calyces combine to form the renal pelvis, which fills the renal sinus.

### Cortical and Juxtamedullary Nephrons

Cortical nephrons start in the outer cortex.
Juxtamedullary nephrons start in the region close to the medulla.
The loops of Henle connect the PCT and DCT. The descending loop dips into the medulla, while the ascending loop returns to the cortex.

### Urinary Bladder

The urinary bladder is a hollow muscular organ storing urine temporarily, holding up to 1 liter.
It is located anterior to the rectum in males and anterior to the vagina and inferior to the uterus in females.
The internal mucosa lining the bladder forms folds called rugae, which disappear as the bladder expands.
The trigone, a triangular area between the ureters and urethra, has smooth and thick mucosa.
The bladder's histology includes:
- Internal mucosa.
- Submucosa.
- Muscularis:
  - Inner and outer longitudinal smooth muscle layers.
  - Middle circular smooth muscle layer.

### Detrusor Muscle

The detrusor muscle, formed by the muscularis, contracts to expel urine from the bladder.

### Urethra

The urethra extends from the bladder base to the body's exterior (3-5 cm in females and 18-20 cm in males).
In males, the urethra is divided into three segments:
- Prostatic urethra: passes through the prostate gland's center.
- Membranous urethra: a short segment passing through the urogenital diaphragm.
- Spongy urethra: extends from the urogenital diaphragm's border to the penis's end.
At the urogenital diaphragm, a circular band of skeletal muscle acts as the external urethral sphincter, controlling urine release. This sphincter is under voluntary control (pudendal nerve) and must be relaxed for micturition (urination).

### Urethra Histology

The inner mucosa (longitudinally folded) consists of:
- Transitional epithelium (stratified at the bladder neck to columnar at the midpoint to stratified squamous near the external opening).
- Lamina propria.
- Mucin-secreting cells in pockets of mucosa.
Females have a smooth muscle layer.
The outer connective tissue layer of the lamina propria anchors the urethra to surrounding structures.

### Renal Physiology

The kidneys have three main functions:
- Excretion of organic waste products from plasma (e.g., urea, creatinine, uric acid).
- Elimination of water and waste into the external environment.
- Homeostatic regulation of plasma volume, osmolarity, pH, and electrolyte levels.
The two kidneys produce urine to accomplish these functions.

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Description

Explore the intricate structure of the kidneys, including their dimensions, tissue layers, and internal anatomy. This quiz covers essential topics such as the renal capsule, adipose capsule, and the kidney's cortex and medulla. Perfect for students studying human anatomy and physiology.