Human Phys Digestion

Oral Cavity

Mouth, cheeks (buccal mucosa), teeth and gums, tongue, hard (boney) and soft (cartilaginous) palate, uvula

Uvula

Aids in saliva production and helps to prevent food and liquids from entering the nasal cavity

Teeth

Function in mastication (chewing)

Incisors, canines, premolars, molars

What are the 4 types of teeth?

Biting; 4

Incisors are made for what? How many do we have on top and bottom?

Ripping; 2

Canines are made for what? How many do we have on top and bottom?

Chewing; 4

Premolars and molars are made for what? How many do we have on top and bottom?

Smooth muscle

What kind of muscle is seen from the esophagus and anus

Sphincters

Specialized segments are divided by

Neutral

What is the pH of the esophagus?

1 to 4

What is the pH of the stomach?

6 to 7.4

What is the pH of the small intestine?

5.7

What is the pH of the cecum?

6.7

What is the pH of the rectum?

Duodenum

The first section of the small intestine, where most chemical digestion occurs.

Jejunum

The second part of the small intestine, located between the duodenum and ileum. It is primarily responsible for the absorption of nutrients and minerals from digested food.

Ilium

The final section of the small intestine that connects to the cecum of the large intestine. It is involved in the absorption of vitamin B12, bile salts, and any remaining nutrients.

Mastication

Chewing, first step in digestion. Breaks food particles into smaller pieces with greater surface area for digestive enzymes to work on

Salivary amylase

Produced by the salavary glands that begins the process of carbohydrate (alpha glucose) digestion by breaking down starches into simpler sugars.

Parotid, submandibular, and sublingual glands

They are major salivary glands in the mouth responsible for producing saliva, which aids in digestion and lubricates food.

Proteins or lipids

No hydrolysis of _____ occurs in the mouth

Cellulose (beta glucose)

Is a polysaccharide that is not digestible by humans due to the lack of necessary enzymes to break down its beta glycosidic bonds. It serves as dietary fiber, aiding in digestive health.

Acid

Salivary amylase is denatured by what

Mouth

The enzyme salivary amylase begins breaking down starch into shorter polysaccharides occurs here

Stomach

Salivary amylase is inactivated and no further carbohydrate digestion occurs here

Small intestines

Majority of starch digestion and breakdown of disaccharides occur here. The enzyme pancreatic amylase breaks down starch into monosaccharides, disaccharides, and oligosaccharides. Is 7m in length (16 to 22 feet), meaning it is small in diameter not length.

Small intestine villi

The digestion of carbohydrates is completed by the enzymes attached to the brush border of the _____. Here the disaccharides and oligosaccharides are broken down into monosaccharides

Large intestine

What functions to partially break down fiber and other indigestible carbohydrates by bacteria to form short chain fatty acids and gas. The remaining fiber is excreted in the feces

Serosa, muscularis, submucosa, mucosa

What are the 4 layers of the GI tract

Serosa

Outer layer of connective tissue

Muscularis

Two layers of smooth muscle responsible for peristalsis and segmentation.

Longitudinal muscle

What is the outer layer of the muscularis

Circular muscle

What is the inner layer of the muscularis

Submucosa

Layers of connective tissue and joins muscularis to mucosa while containing blood vessels, nerves, and lymphatics.

Mucosa

Non-kerotinized stratified squamos epithelial cells for protection, abrasion and acid reflux

Peristalsis

Wave like contractions that move the food bolus towards the stomach

Myogenic and neurogenic

What are the 2 control systems of peristalsis

Myogenic

Signals between smooth muscle cells

Neurogenic

Signals from nervous system

Primary peristalsis

Starts when food bolus enters

Behind bolus

Circular muscle and longitudinal muscle contracts _____ (behind or in front bolus)

In front bolus

Longitudinal muscle relax _____ (behind or in front bolus)

Secondary peristalsis

Stretch receptors signal a second wave of contractions

Lower esophageal sphincter

High pressure stimulates (stretching) and opening (last 2-4 cm)

Reverse peristalsis

Vomiting caused by reverse of involuntary smooth muscle contractions caused by poisoning (food or toxins) or bacteria

Fundus, body and pylorus

Three regions of the stomach

Cardioesophageal sphincter and pyloric sphincter

What are the 2 valves of the stomach

Protein digestion

The mucosa is specialized for what

Gastric Rugae

Folds that allow the stomach to expand and increase the surface area of the stomach

Cardioesophageal sphincter

The esophagus is superior to what sphincter

Pyloric sphincter

The muscle that controls the passage of food from the stomach to the small intestine. First segment of the small intestine (25 to 30 cm in length)

G-cells

These cells secrete gastrin

Gastrin

Stimulates parietal cells to produce HCL

Chief cells

These cells secrete pepsinogen (inactive protease), which is converted to pepsin in the stomach.

Zymogens

Inactive precursors of enzymes that require biochemical change

Pepsinogen

A zymogen, inactive form of the enzyme pepsin

Peptides and amino acids

Proteins are enzymatically broken down into

Chyme

When ingested food is mixed with gastric secretions by mixing movements of the stomach, a thick liquid mixture known as ____ is produced and emptied into the duodenum

Carbohydrates and lipids

No digestion of ______ occurs in the stomach

Outer longitudinal, inner circular, inner longitudinal

What are the three muscle layers of the pyloric sphinter

Secretin and cholecystokinin

Acidic chyme and fatty/proteins stimulates the release of______

Secretin

Hormone that stimulates release of pancreatic juice containing bicarbonate buffer. Stimulates increased bile production in the liver

Cholecystokinin

Stimulates release of pancreatic juice, gastric motility and satiety. Stimulates increased contraction of the gallbladder and release of bile into the duodenum and is released by amino acids

Microvilli

Increase the surface area of epithelial cells lining the small intestine, thus increasing absorption (surface is known as the brush border)

Enterocytes

Absorbs ions by active transport, which facilitates water absorption

Lacteal

Extensions of the lymphatic system into epithelial microvilli. Function in the absorption of lipids and proteins

Goblet cells

Secrete mucous that lubricates the digestive tract

T cells

Are part of the immune cells

Enteroendocrine cells

Produce digestive hormones

Brush boarder enzymes

Aid in digestion and absorption of carbohydrates, proteins and lipids

Lipid emulsification and absorption

What happens to lipids in duodenum

Liver

Produces bile

Gallbladder

Stores bile

Trypsin

Cuts next to the amino acid lysine

Chymotrypsin

Cuts next to carboxyl (C terminus) side of some amino acids

Aminopeptidase

Cuts next to amine end (N terminus)

Carboxypeptidase

Cuts single amino acids off branched chain amino acid

Colon

Part of the large intestine (150 cm; 5 feet) that absorbs water and forms waste. It is large in diameter in length and no enzymes are produced

Water and electrolyte absorption, feces storage, bacterial fermentation

What are the functions of the colon

Water and salt absorption, maintain gut flora

What is the function of the cecum

Appendix

Part of the lymphatic system destroys bacteria before it is absorbed

Vibrio cholera

Transmitted through fecal contamination of water, permanently binds to large intestine, survives acid stomach, prevents water reabsorption in intestines, leads to diarrhea (10-20 liters of diarrhea a day), death by dehydration, genetically linked to type O blood making them more susceptible