Human Digestion

Biology 11

organ systems

cells

tissues

organs

organ systems

organism

uvula, tongue, papallie, taste buds

uvula: small tissue projection that hangs from the soft palate, helps with speech

tongue: covers the floor of the oral cavity, aids in moving food during mastication (chewing) and degulition (swallowing)

papallie: small raised bumps, contain taste buds

taste buds: located on tongue and cheeks, sweet, sour, salty, bitter, umami

mechanical digestion

physical breakdown of the food begins with teeth, griniding food, increasing surface area

mucus is added for easier swallowing

bacteria in the mouth feed off nutrients

scope + biopsy

• scope: camera medical tool that can be used to view things such as stomach ulcers

• biopsy: the removal of tissye from any part of the body to examine it for disease

four components of digestion

• Ingestion – this is the consumption of or taking in of nutrients.

• Digestion – the chemical breakdown of large organic molecules into smaller components by enzymes.

• Absorption – the transport or delivery of digested nutrients to body tissues.

• Egestion – the elimination of food waste materials from the body.

saliva

released from the salivary glands and begins chemical digestion of starches

contains the enzym salivary amylase which breaks down starches into simpler cards

moistens + lubricates food, making it easier to swallow

bolus

the lubricated ball of food that is swallowed

stomach sphincters

top: cardiac/esophagal sphincters

• allows food from esophagus to enter and prevents food from going back up into the esophagus

bottom: pyloric sphincter

• slowly releases partially digested food (chyme) into the small intestine

esophagus

• bolus of food moves down the esophagus

• peristalisis is the wave-like muscular contraction that propels the bolus down

• 25cm long

oral cavity

• The gastrointestinal tract (GI tract) begins with the oral cavity.

• Oral (or/o = pertaining to the mouth)

• The cheeks form the walls of the oval shaped oral cavity, and the lips surround the opening of the cavity.

• The hard palate form the anterior portion of the roof of the mouth. 

• The soft palate consists of the muscular membrane that lies posterior to it. 

alimentary canal

• The human digestive tract is often referred to as the alimentary canal.

• The alimentary canal of a normal adult is approximately 6.5 to 9 meters long.

• It runs from mouth to anus!

salivary glands

• 3 pairs in the oral cavity

• Produce Saliva, that contain digestive enzymes. 

• Saliva is released from the parotid gland, submandibular gland and sublingual gland on EACH side of the mouth. 

• Narrow ducts carry saliva into the oral cavity. 

stomach

• food stays here for 4h

• it can expand to hold 1.5l

• initial site of protein digestion

• partially digested food is called chyme

small intestine

• dueodenum, jejunum, ileum

• 7m long

• most digestion and absorption takes place in the duodenum

large intestine

• also called the colon.

• stores food waste long enough so that water can be reabsorbed from it before it exits the body.

• Along with the water, some inorganic salts, minerals and vitamins are also absorbed

• 1.5 m long

Prosecretin (inactive form) / Secretin (active form)

• duodenum secretion

• The small intestine duodenal cells secrete prosecretin hormone and when mixed with acid chyme it becomes secretin. 

• Secretin regulates secretions from the stomach, pancreas and liver.

• Stimulates the pancreas to release bicarbonate solution to neutralize the acid chyme

Bicarbonate ion solution

• pancreas secretion

• Neutralizes the acidic chyme.

• Raises pH from 2.0 to 9.0

Trypsinogen (inactive form)

Trypsin (active form)

• pancreas secretion

• Protein digesting enzyme

• Trypsinogen is converted to Trypsin which breaks down large protein chains into smaller ones (polypeptides).

eripsens

• pancreas secretion

• Breaks down smaller protein chains (polypeptides) into individual amino acids.

Pancreatic Amylase 

• pancreas secretion

• Break complex carbs into smaller chains called disaccharides.

Disaccharide enzyme 

• pancreas secretion

• Breaks disaccharide carbs into individual monosaccharides (simple sugars).

Lipases (lipid/fat digestion)

• pancreas secretion

• Enzymes that break down fats into individual fatty acids and glycerol.

the liver

• is able to detoxify many substances in the bofy

• constantly produces bile, stored in the gall bladder

bile

The presence of lipids in the small intestine triggers the release of cholecystokinin (CCK) from the small intestine, which triggers release of bile from the gallbladder. 

Bile fluid contains salts that emulsify fats. Emulsification means breaking fats into smaller droplets that can be absorbed and digested. 

gallbladder

• stores bile from the liver

• gallstones cause: The cholesterol contained in the bile acts as a binding agent and causes the bile salts to crystallize into gallstones (that can block the duct and cause great pain to the person).

villi

The small intestine is lined with millions of small finger-like projections known as villi which are responsible for absorption of nutrients in the small intestine. They increase the surface area of the small intestine.

each villus contains:

a capillary network

• end products of protein and carb digestion enter the capillary network

a lacteal

• end products of fat digestion are absorbed into the lacteal