Structure Final New

What are the four layers of the alimentary canal wall?

Mucosa, submucosa, muscularis externa, and serosa/adventitia.

What is the function of the mucosa?

It is responsible for absorption and secretion.

What is the function of the submucosa?

It contains connective tissue, blood vessels, glands, and nerves.

What is the function of the muscularis externa?

It is responsible for GI motility.

What is the function of the serosa/adventitia?

It provides outer protection and structural support.

Where is the myenteric plexus located?

In the muscularis externa.

What does the myenteric plexus control?

GI motility, including peristalsis and segmentation.

What is peristalsis?

Wave-like contractions that move food forward.

What is segmentation?

Mixing contractions that improve digestion.

What triggers the cephalic phase?

Sight, smell, or thought of food.

What system mediates the cephalic phase?

The vagus nerve (parasympathetic nervous system).

What happens during the gastric phase?

Food in the stomach stimulates acid and enzyme secretion.

What hormone is released during the gastric phase?

Gastrin.

Which cells secrete intrinsic factor?

Parietal cells.

What is the function of intrinsic factor?

It allows vitamin B12 absorption.

Where is vitamin B12 absorbed?

In the terminal ileum.

What triggers release of CCK?

Chyme entering the duodenum.

What does CCK do to the gallbladder?

Stimulates contraction.

What does CCK do to the pancreas?

Stimulates enzyme secretion.

What effect does CCK have on the stomach?

Slows gastric emptying.

What enzyme activates trypsinogen?

Enteropeptidase.

What is trypsinogen converted into?

Trypsin.

What is the role of trypsin?

Activates other digestive enzymes.

What is bile's role in fat digestion?

It emulsifies fats.

What are bile salts recycled through?

Enterohepatic circulation.

What is the hepatic portal system?

A system that carries blood from the GI tract to the liver.

Why is the hepatic portal system important?

It allows nutrient processing and detoxification.

What is gluconeogenesis?

Production of glucose from non-carbohydrate sources.

Name one substrate for gluconeogenesis.

Amino acids.

What force drives glomerular filtration?

Glomerular hydrostatic pressure.

Why can't albumin be filtered?

It is too large.

What is the juxtaglomerular apparatus?

A structure that monitors sodium and blood pressure.

What part of the JGA senses sodium?

Macula densa.

What do JG cells release?

Renin.

When is renin released?

When blood pressure or sodium is low.

What pathway does renin activate?

RAAS.

What does RAAS produce?

Angiotensin II.

What does angiotensin II do?

Causes vasoconstriction.

What hormone does angiotensin II stimulate?

Aldosterone.

What does aldosterone do to sodium?

Increases reabsorption.

What does aldosterone do to potassium?

Increases excretion.

What is ADH?

Antidiuretic hormone.

What does ADH do?

Increases water reabsorption.

How does ADH increase water reabsorption?

By inserting aquaporins in the collecting duct.

Where does bulk reabsorption occur?

Proximal convoluted tubule.

What percent of glucose is reabsorbed in the PCT?

Nearly 100%.

What does the descending limb reabsorb?

Water.

What does the ascending limb reabsorb?

Solutes.

What gradient is created in the nephron loop?

Medullary osmotic gradient.

What is the vasa recta?

Capillaries that preserve the gradient.

What mechanism does the vasa recta use?

Countercurrent exchange.

Where does fine-tuning of urine occur?

Distal convoluted tubule and collecting duct.

What is creatinine?

A waste product used to estimate GFR.

Why is creatinine useful for GFR?

It is filtered but not reabsorbed.

What is ANP?

Atrial natriuretic peptide.

What does ANP do?

Promotes sodium excretion and lowers blood pressure.

What do Sertoli cells form?

Blood-testis barrier.

What is the function of the blood-testis barrier?

Protects sperm from immune attack.

What hormone do Sertoli cells produce?

Inhibin.

What does inhibin do?

Inhibits FSH.

What do Leydig cells produce?

Testosterone.

What hormone stimulates Leydig cells?

LH.

What is spermiogenesis?

Transformation of spermatids into sperm.

Where do sperm gain motility?

Epididymis.

What are sperm?

Male reproductive cells.

What is semen?

Fluid containing sperm and gland secretions.

Name one gland that contributes to semen.

Seminal vesicles.

Name another gland that contributes to semen.

Prostate gland.

Name a third gland that contributes to semen.

Bulbourethral glands.

How do kidneys regulate electrolytes?

Through hormones like aldosterone.

What electrolytes does aldosterone regulate?

Sodium and potassium.

How do kidneys regulate pH?

By reabsorbing bicarbonate and excreting hydrogen ions.

What condition can vomiting cause?

Metabolic alkalosis.

What condition can diarrhea cause?

Metabolic acidosis.

What protein maintains oncotic pressure?

Albumin.

Where is albumin produced?

Liver.

What happens if albumin is low?

Filtration balance is disrupted.

What is the gastrocolic reflex?

Colon activity increases after stomach distension.

What is transport maximum?

Maximum reabsorption capacity.

What happens when Tm is exceeded?

Substance appears in urine.

Give an example of Tm being exceeded.

Glucose in diabetes.

What is the function of the dartos muscle?

Wrinkles scrotal skin.

What is the function of the cremaster muscle?

Raises and lowers testes.

Why must testes be temperature regulated?

For proper sperm production.