CH 41 - GOT FAT?
Villi and Microvilli
- folds inside the small intestine that increase the surface area for absorption - many blood vessels go to them - molecules are absorbed into blood stream - increase surface area of intestine to allow for optimal absorption
List major secretions that enter duodenum and where they come from
- inactive proteases from pancreas - bile from liver - acid chyme from stomach
Two major functions of the small intestines
- most chemical digestion - digested food is sent to blood
What two major changes occur to food in the mouth?
1- it is cut/pulverized into smaller pieces 2- salivary amylase begins polymer breakdown
List three functions of the hydrochloric acid/HCl of the stomach
1- kills pathogens/microbes 2- pH2 → effective pepsin breakdown of proteins 3- emulsify food and protect against bacteria
Overview of Food Processing! 👄🍕
1. Ingestion 2. Digestion (through enzymatic hydrolysis, extra/intracellular feeding, or alimentary canals) 3. Absorption (cells take up small molecules) 4. Elimination (removal of undigested material 💩)
Essential Amino Acids
8 amino acids that must be obtained in a diet
Hepatic portal vessel
A large circulatory channel that conveys nutrient-laden blood from the small intestine to the liver, which regulates the blood's nutrient content
Intracellular feeders
Break down food inside cells
Extracellular feeders
Break down food outside cells
Undernourishment
Caloric deficiency
Alimentary canals
Digestive track
In the Small intestine...
Duodenum, bile
Bulk-feeders
Eat large pieces of food
Malnourishment
Essential nutrient deficiency
Over-nourishment
Excessive food intake
In the Stomach...
Gastric juice, pepsin(active)/pepsinogen(inactive), acid chyme, pyloric sphincter
Opportunistic Feeding
Herbivore 🐄, Omnivore 💃, Carnivore 🐆
Minerals
Inorganic cofactors
Distinguish between intracellular digestion and extracellular digestion.
Intracellular - happens inside the cell Extracellular - happens outside the cell (like the breaking down of food through gastric acid/contraction of smooth muscle)
Breaking those Nucleic Acids down!
LUMEN OF SMALL INTESTINE DNA+RNA → (pancreatic nucleases) → nucleotides EPITHELIUM OF SMALL INTESTINE Nucleotides → (nucleotidases) → nucleosides → (nucleotidases and phosphatases) → nitrogenous bases, sugars, phosphates
Breaking those Fats down!
LUMEN OF SMALL INTESTINE Fat globules → (Bile salts) → Fat droplets →(pancreatic lipase) → glycerol, fatty acids, glycerides
Substrate-feeders
Live in/on food
Essential nutrients
Materials that must be obtained in preassembled form
How is the stomach itself protected from being digested of damaged by pepsin or HCl?
Mucous layer of cells lines the lumen and constantly replace themselves
Breaking those Carbs down! 🍞
ORAL CAVITY 👅 Polysaccharides → (salivary amylase) → smaller polysaccharides LUMEN OF SMALL INTESTINE Polysaccharides → (pancreatic amylase) → disaccharides EPITHELIUM OF SMALL INTESTINE Disaccharides → Monosaccharides
Vitamins
Organic coenzymes
heterotrophs
Organisms that cannot make their own food
Autotrophs
Organisms that make their own food
How does food move down the esophagus?
Perystalsis (rhythmic waves of contraction by smooth muscle)
Peristalsis
Rhythmic waves of contraction by smooth muscle
Sphincters
Ring-like valves that regulate passage of material
Breaking those Proteins down! 🍖
STOMACH Protein → (Pepsin) → smaller polypeptides LUMEN OF SMALL INTESTINE More Polypeptides → (trypsin and chymotripsin) → smaller polypeptides All those small polypeptides → (carboxypeptidase) → amino acids EPITHELIUM OF SMALL INTESTINE Small proteins and amino acids → (dipeptidases, carboxypeptidases,and aminopeptidases) → amino acids
In the Oral cavity...
Salivary amylase, bolus, pharynx, epiglottis, esophagus
Accessory glands 👜👒
Salivary glands, pancreas, liver, gall bladder
Suspension-feeders
Sift food from water 🐋
Fluid-feeders
Suck fluid from host 🕷
How are the parietal cells of the stomach protected from digesting themselves by pepsin?
The stomach is protected by the epithelial cells, which produce and secrete a bicarbonate-rich solution that coats the mucosa. Bicarbonate is alkaline, a base, and neutralizes the acid secreted by the parietal cells, producing water in the process. This continuous supply of bicarbonate is the main way that your stomach protects itself from autodigestion (the stomach digesting itself) and the overall acidic environment.
Sphincters in the digestive system
They act as valves to control the flow of partially digested food
Salivary glands 👅
Tongue, parotid gland, sublingual gland, submandibular gland
Essential fatty acids
Unsaturated fatty acids
gastric inhibitory peptide (GIP)
decreases stomach churning → slows emptying of stomach
Evolutionary Adaptations of recent digestive systems?:
dentition (teeth assortment), length of digestive track, symbiosis (with the bacteria in our intestines), ruminants (multiple stomachs of cows/other animals with multiple stomachs)
Mechanisms of absorption of different nutrients by small intestines
diffusion - fat molecules sodium in/dependent transporters - sugars and amino acids chylomicrons - fats
nutritional adaptation of animals that practice coprophagy
feces of large herbivores contain substantial amts of semi-digested foods
Regulation of blood glucose levels
if too low: liver converts glycogen to glucose and then releases glucose into bloodstream if too high: insulin is released and glucose is converted to glycogen for storage
where are fats digested?
lumen of the small intestine
Lacteal
lymphatic capillary that absorbs dietary fats in the villi of the small intestine
where are carbs digested?
mouth and small intestine
Explain the adaptation that protects the pancreas from digesting itself by the peptidases it produces
pancreatic enzymes are only activated once in the small intestine
What is the function of the epiglottis?
prevent mixing of food and air cavities
why are essential nutrients "essential"?
since they cannot be created in the body, they must be consumed
where are nucleic acids digested?
small intestine
cholecystokinin (CCK)
stimulates release of digestive enzymes to pancreas; emptying bile in gall bladder
Gastrin
stimulates release of gastric acid
secretin
stimulates secretion of sodium bicarbonate to pancreas and bile to liver
where are proteins digested?
stomach and small intestine
coprophagy
the eating of own feces
Why must animals eat food?
they cannot make their own food for energy
Adaptations of the small intestines that enhance its function
villi and microvilli absorb nutrients and send them to blood; epithelial tissues secretes mucous and enzymes