L12 physiology

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Questions and Answers

What is the effect of decreased sodium chloride concentration on the afferent arterioles?

Decreases resistance to blood flow (correct)

Decreases glomerular capillary hydrostatic pressure

Increases resistance to blood flow

Causes constriction of the arterioles

Which muscle is primarily responsible for bladder contraction during micturition?

Internal urethral sphincter

External urethral sphincter

Pelvic floor muscles

Detrusor muscle (correct)

What triggers the micturition reflex to initiate urination?

Contraction of the external urethral sphincter

Increased sodium concentration in the blood

Stretch receptors in the bladder wall (correct)

Release of renin from juxtaglomerular cells

During which phase does the internal urethral sphincter remain tense?

Storage phase Signup and view all the answers

What must occur for urination to successfully take place?

Coupling of micturition reflex with relaxation of external urethral sphincter Signup and view all the answers

What structures are involved in the filtration process of a nephron?

Glomerulus and peritubular capillaries Signup and view all the answers

Which segment of the Loop of Henle primarily consists of simple squamous cells?

Thin segment Signup and view all the answers

What is the primary function of the distal convoluted tubule (DCT)?

Secretion of ions and other substances Signup and view all the answers

What is the role of juxtaglomerular cells within the juxtaglomerular apparatus?

Secreting renin Signup and view all the answers

Which process involves the movement of substances from renal tubules back into blood plasma?

Tubular reabsorption Signup and view all the answers

What is the primary function of the kidneys?

Excretion of waste products and foreign chemicals Signup and view all the answers

Which part of the nephron is responsible for the initial filtration of blood?

Glomerulus Signup and view all the answers

What does GFR stand for in the context of kidney function?

Glomerular Filtration Rate Signup and view all the answers

Which of the following components is part of the renal tubule?

Loop of Henle Signup and view all the answers

What role does the hormone erythropoietin play in the body?

Regulation of red blood cell production Signup and view all the answers

Which factor is NOT a function of the kidneys?

Storing bile Signup and view all the answers

What is the primary role of the proximal convoluted tubule (PCT)?

Reabsorption of water and solutes Signup and view all the answers

What anatomical feature encloses the glomerulus?

Bowman's capsule Signup and view all the answers

Study Notes

Renal System Overview

The kidney is a reddish-brown, bean-shaped organ, approximately 12 centimeters long, enclosed in a tough fibrous capsule.
Kidneys are located on either side of the vertebral column, behind the peritoneum, against the deep muscles of the back.
Kidneys perform crucial functions including excretion of waste products and foreign chemicals; regulation of water and electrolyte balances; regulation of body fluid and electrolyte concentrations (Na+, Ca2+, K+, etc.); regulation of arterial blood pressure via the renin-angiotensin system; regulation of acid balance; secretion, metabolism, and excretion of hormones; hemopoietin function (regulation of red blood cell production via erythropoietin); and aiding in vitamin D production.

Kidney Structure

The kidney has distinct regions:
- Renal cortex
- Renal medulla
- Renal pyramids
- Renal pelvis
- Renal capsule
- Ureter

Nephron

The nephron is the structural and functional unit of the kidney.
Each nephron has two components:
- Vascular component
- Tubular component
Cortical nephrons (80-85%) are more superficial and have a shorter loop of Henle.
Juxtamedullary nephrons (15-20%) are located closer to the medulla and possess a longer loop of Henle, essential for concentrating urine.

Renal Corpuscle

The renal corpuscle, the initial filtering unit, is composed of:
- Glomerulus: A network of capillaries
- Bowman's capsule: A cup-shaped structure that encloses the glomerulus

Renal Tubule

The renal tubule, extending from Bowman's capsule, processes the filtrate:
- Proximal convoluted tubule (PCT): Reabsorbs water and solutes, secretes substances.
- Loop of Henle: A hairpin loop with ascending and descending limbs; crucial for water reabsorption and urine concentration.
- Distal convoluted tubule (DCT): Primarily involved in secretion.
- Collecting ducts: Receive filtrate from DCTs, empty into minor calyces.

Capillary Beds

Each nephron includes two capillary beds:
- Glomerulus - filters blood
- Peritubular capillaries - reabsorb and secrete substances

Urine Formation

Urine formation involves three processes:
- Glomerular filtration: Substances move from glomerular capillaries into renal tubules.
- Tubular reabsorption: Useful substances are reabsorbed into the blood.
- Tubular secretion: Additional wastes move from the blood to the filtrate.

Juxta-Glomerular Apparatus

The juxtaglomerular apparatus (JGA) is a specialized region near the glomerulus in the kidney, regulating glomerular filtration rate (GFR) via:
- Macula densa cells
- Extra glomerular mesengial cells
- Juxtaglomerular cells: Secrete renin.

Micturition

Micturition is the process of emptying the urinary bladder.
It is controlled by autonomic and somatic nervous systems.
The internal urethral sphincter remains tense during storage phase.
Relaxation of the sphincters and contraction of detrusor muscle cause urination.
Micturition is initiated by stretch receptors in the bladder wall.

Learning Resources

Essential textbook for anatomy and physiology is recommended (Marieb En, Human Anatomy and Physiology, 9th Ed.)

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