Human Physiology: The Digestive System

Flashcards covering key concepts and functions of the digestive system, including organs, processes, and absorption mechanisms.

What are the learning outcomes related to the digestive system?

Organs of the gastrointestinal tract and accessory organs, and their basic functions.

How does the epithelial layer vary in the GI tract?

The structure and function of the epithelial layer differs in different parts of the GI tract.

What nutrients are needed for normal function, growth & repair of tissues?

CHO, fats, proteins (macronutrients), vitamins, minerals and water

What are the components of the digestive system?

Oral cavity, teeth, tongue, salivary glands, pharynx, esophagus, stomach, pancreas, liver, gallbladder, small intestine, large intestine, anus.

What are the six basic processes performed by the GI tract?

Ingestion, mechanical digestion, chemical digestion, secretion, absorption, and excretion.

What are the four main layers of the GI tract wall?

Mucosa, submucosa, muscularis, and serosa.

Describe the Mucosa layer of the GI Tract wall

Inner layer; epithelium for absorption and secretion; connective tissue, blood vessels, inner muscular layer.

Describe the Submucosa layer of the GI Tract wall

Connective tissue, large blood and lymphatic vessels, submucosal plexus (controls secretions of GI tract).

Describe the Muscularis layer of the GI Tract wall

Smooth muscle layer (inner circular and outer longitudinal layers).

Describe the Serosa layer of the GI Tract wall

Outer layer; forms the mesentery where nerves & blood vessels enter and leave the gut.

What are the main Hormones that control the GI Tract?

Gastrin, cholecystokinin (CCK)

What is the Function of the mouth in the GI System?

Mastication (mechanical digestion), mixes with saliva, forms a bolus for swallowing

What are the three pairs of salivary glands and what do they produce?

Submandibular, parotid, sublingual glands. They produce 1.0–1.5 liters of saliva/day.

What type of epithelium is the Oesophagus made up of?

Stratified squamous epithelium.

What is the structure and function of the oesophagus?

Collapsible muscular tube; transports food to the stomach; bolus propelled by peristalsis.

What are The 4 main functions of the stomach

Stores food, mechanical digestion, chemical digestion, production of intrinsic factor (Vit B12 absorption).

What are the four regions of the Stomach?

Cardiac, fundus, body, pylorus.

What is the digestion process like in the stomach?

Pepsinogen --(HCl)--> pepsin.

What are the three segments of the Small Intestine?

Duodenum, jejunum, ileum.

What is the main function of the small intestine?

Digestion & absorption of nutrients and water (90% of absorption here).

What is the Function of the duodenum?

Mixes chyme with pancreatic & liver/gallbladder secretions; neutralizes stomach acid.

What is the Function of the Jejunum?

Most digestion and absorption of nutrients takes place here.

What is the Function of the Ileum?

Specialist function; absorbs vitamin B12 & bile salts.

What increases the surface area for absorption in the small intestine?

Plicae circulares, villi, microvilli.

What is the function of the intestinal glands (crypts of Lieberkuhn)?

Secrete intestinal juice (water & mucus), endocrine cells secrete hormones (CCK & secretin).

What is the function of Brunner's Glands?

Produce alkaline mucus to neutralize acidic chyme from stomach; only in duodenum.

What does coeliac disease cause?

Autoimmune disease -> flattened villi -> reduced absorptive surface -> malabsorption of nutrients.

describe Peristalsis

Propulsive.

What is Segmentation?

Churn and fragment bolus, non-propulsive; mixes contents with intestinal secretions.

How are carbohydrates digested in the small intestine?

Amylase (salivary glands & pancreas) breaks down polysaccharides to disaccharides then Brush border enzymes break down disaccharides to monosaccharides.

How are Proteins digested in the small intestine?

Pepsin (stomach) breaks down Proteins & Large polypeptides to Peptides, then Pancreatic proteases and Brush border enzymes break down Peptides to Amino acids

What is required for dietary fats (triglycerides) to be broken down?

Mechanical stomach action creates large fat droplets. Bile salts emulsify into smaller droplets -> increases surface area for lipase to act

What does the pancreatic lipase break Triglycerides into?

Monoglyceride + 2 free fatty acids.

What happens after bile breaks down fats into smaller droplets?

Micelles -> Diffuse to mucosa-> FA & monoglyceride diffuse into epithelial cell by simple diffusion.

How are nutrients absorbed in the small intestine?

Active or passive transport.

Where does absorption mainly take place?

90% of absorption occurs in SI (mainly jejunum).

How are Glucose/galactose and Fructose absorbed?

Facilitated diffusion or Co-transport+ Na+.

What happens within epithelial cells to re-form triglycerides?

Re-form triglycerides from monoglycerides & free fatty acids, coated with protein to form chylomicrons . Chylomicrons enters Lacteals (lymphatics) -> Systemic circulation