nutrition exam 1

Auto-enzymatic digester

animals whose digestion of feed depends on endogenous secreted into the GIT

Allo-enzymatic digester

animals whose digestion of feed depends on both endogenous enzymes and microbial enzymes from microbes that inhabit the GIT

Allo-enzymatic digesters depend on

microbial fermentation of plant materials as a source of energy

Non-ruminant characteristics

single stomach, limited storage capacity in stomach, limited microbial fermentation in stomach, limited microbial fermentation in the hindgut,fast passage rate through the GIT, and must feed concentrated and well-balanced diets

Non-ruminant herbivore characteristics

hindgut fermenter, single stomach, limited feed storage in stomach, limited microbial fermentation in the stomach, extensive fermentation in the hindgut, fast passage rate through the stomach and small intestine, and slow passage rate through the large intestine

Ruminant characteristics

compartmentalized stomach (four chambers) high feed storage capacity in stomach, extensive microbial fermentation in stomach, slow passage rate through the GIT, further categorized into grzers and browsers, and microbes have first claim on any ingested feed

What are some major segments of the gastrointestinal tract?

stomach, liver, duodenum, pancreas, small intestine, caecum, colon, rectum

Mouth

Teeth and saliva

Teeth

Chewing to breakdown feed and stimulate secretion of saliva and lubricate ingested feed. this created a bolus. Chewing helps detection of inedible substances

incisor

cutting and clipping feed. ruminants lack upper ones

canine

tearing, piercing, and holding feed prominant in carnivores; reduced or absent in herbivores

premolar and molar

grinding and crushing feed

carnassial

shearing feed and modified premolar and molar

Saliva

secreted by parotid gland, submandibular gland, sublingual gland. composed of water enzymes and minerals and mucus. medium for perceiving taste

Esophagus

muscular tube that connects the throat to the stomach. Transports feed bolus to the stomach after swallowing through peristalsis

Upper esophageal sphincter

controls entry from throat

lower esophageal sphincter

controls entry into stomach and prevents reflux

esophagus in ruminants

bidirectional movement for ruminantion

esophagus in horses

strong lower esophageal sphincter not able to vomit

esophagus in poulty

leads to crop before the stomach

Stomach

muscular organ located between the esophagus and small intestine. recieves undigested bolus from the mouth and esophagus. resleases partially digested feed (chymes) into the small intestine

Stomach functions

Storage of feed, secretion of digestive enzymes and gastric acid, feed digestion, protection, absorption, and hormone production

fundus

stores feed and gas. stimulates gastric contractions

cardia

connects to esophagus to stomach

body (corpus)

feed mixing and digestion

pylorus

connects stomach to small intestine

mucosal surface cell

line surface of stomach and gastric pits and produce alkaline mucus

mucosal neck cell

line the upper part of the gastric gland and produce alkaline mucus

cheif cell

pepdinogen (protein digestion)nand gastric lipase (fat digestion)

parietal cell

=oxyntic cell. HCL to acidic conditions denatures protein and activates pepsinogen. intristic factor

enteroendocrine cell

G-cells, located mainly within gastric glands of the pylorus. prodouces and releases gastrin.

gastric stem cells

proliferation and differentiation into other cells types of the stomach epithelium. repair and regeneration

Small intestine

long, coiled tube in the gut where most nutrient digestion and absorption occurs

mesentery

connective tissue that attaches the small intestine to the abdominal wall and supplies the small intestine with blood vessels, lymphatics, and nervess

small intestine segments

enzymatic digestion, nutrient absorption, hormone secretion, immune function (GALT) and motility

GALT

gut-associated lymphoid tissue

Duodenum

proximal and shortest segment of the small intestine. main site that receives chyme from the stomach and mixes chyme with digestive juices

jejunum

second and longest of the small intestine. main site for enzymatic digestion and absorption.

Ileum

distal segment of the small intestine. main site for absorption of remaining nutrients and passes chyme to the large intestine. substantial Galt presence

Cecum

blind pouch, located at the junction of the small and large intestine, entry point for chyme from the small intestine

colon

main section of the large intestine

Large intestine functions

nutrient absorptions, feces formation and storage, microbial fermentation, vitamin synthesis, and immune function and barrier protection

large intestine nutrient absorption

absorbs remaining water and electrolytes from undigested feed, and concentrates waste into solid feces

large intestine feces formation and storage

converts semi-liquid chyme from the small intestine into solid fecal matter. stores feces in the rectum until defecation

Large intestine microbial fermentation

hindgut microbes break down and ferment undigested feed and produce VFAs

What are the four layers that form the gut?

Mucosa, submucosa, muscularis, serosa

mucosa in the stomach

deep gastric pits, glands that secrete acid and ezymes. lines by mucus-secreting cells to protect from acid

muscularis in stomach

has three layers of muscle

small intestine mucosa

has villi and microvilli to increase surface area for absorption. has intestinal glands

small intestine muscularis

two muscle layers

large intestine mucosa

no villi, many goblet cells for mucus secretion.

large intestine muscularis

outer longitudinal layer forms three bands

What factors contribute to the very large absorptive surface area of the small intestine?

length, circular folds, villi, and microvilli

How is the pancreas organized?

exocrine and endocrine pancreas

Exocrine pancreas

production and secretion of digestive enzymes and bicarbonate into the duodenum. acinus, duct cells, pancreatic juice, this makes up 98% of total pancreas mass

acinus

cluster of acinar cells that produce and secrete inactive digestive enzymes into the pancreatic duct

duct cells

produce and secrete bicarbonate that neutralizes incoming gastric acid and maintains alkaline pH in the small intestine

pancreatic juice

inactive digestive enzymes +bicarbonate buffer

endocrine pancreas

secretion of hormones into circulation. a-cells, B-cells, Pancreatic islet. makes up 2% mass

a-cells

produce glucagon in response to low blood glucose

B-cells

produce insulin in response to high blood glucose

pancreatic Islet

collection of a-cells, B-cells, and other hormone-producing cells

liver organization

portal triad: portal vein (~75%), hepatic artery (~25%), and bile duct

liver functions

bile production and secretion, carbohydrates = maintain energy supply, amino acid metabolism= eliminate excess nitrogen, lipid metabolism=maintain energy supply, vitamin and mineral storage, and neutralization of gut-derived toxins, systemic toxxins, drugs, and xenobiotics

“general function” of gastrointestinal hormones

regulate secretion of gastric acid, digestive enzymes, bile, and bicarbonate. control gastric emptying and gut motility. coordinate nutrient sensing among the gut, liver, pancreas, and other organs. gut hormones are generally short-lived in circulation

gastrin function and stimuli

f: increase gastric acid release and increase gastric motility. S: stomach distension

Cholecytokinin function and stimulus

F; increase pancreatic enzyme release, increase bile release, increase gastric emptying. S: amino acids and fatty acids in duodenum.

Secretin function and stimuli

F; Increase in bicarbonate release and decrease in gastric acid release

Somatostatin function and stimuli

F: decrease in gastrin release, decrease in CCK release, decrease in secretin release. S; acidic chyme in duodenum gastrin, CCK

Pig gut structure

monogastric omnivore stomach: simple, single-chambered stomach. secretes acid and enzymes to digest both plant and animal material. large intestine: well developed cecum and colon for fermentation of fiber, but not as extensive as in herbivores. can absorb water and some VFAs

Dog and Cat gut structure

monogastric carnivore. Stomach: simple stomach, very acidic. specialized for digesting meat and protein-rich diets. Large intestine: short, limited fermentation. Main role is water and electrolyte absorption

horses gut structure

hindgut fermenters. stomach: simple and small relative to body size limited storage, must eat small, frequent meals. Large intestine: huge cecum and colon, main sites of microbial fermentation of fiber. produces volatile fatty acids for energy.

poultry gut structure

stomach: two parts Proventriculus: glandular stomach that secretes digestive enzymes. Gizzard: muscular part that grinds food. Large intestine: very short, includes two ceca, where some fermentation occurs. main role water reabsorption

Ruminants gut structure

foregut fermenters. Stomach: four compartments, Large intestine: some additional fermentation in the large intestine but minro compared to the rumen. Water absorption is significant

what are the four chambers of the ruminant stomach

rumen, reticulum, omasum, abomasum

rumen

largest chamber, lines with papillae that increase surface area for absorption. contain billions of microbes. primary fermentation vat where microbes break down plant fibers. Produces VFAs and methane and CO2

Reticulum

honeycomb-like structure on the inner surface. located next to rumen. catches dense materials. works with the rumen in mixing and regurgitation during rumination. Starts forming food boluses

omasum

lined with many thin tissue folds. absorbs water and materials from the digesta. filters large particles, allowing only finely digested material to pass to the next chamber

Abomasum

the “true stomach”, glandular. secretes HCl and digestive enzymes. digests microbial protein and any remaining feed particles. prepares nutrients for absorption in the small intestine.

what are ruminant pillars

muscular ridges or folds found on the inner wall of the rumen

what are ruminal pillars function

divide the rumen into sacs. aid in rumen contractions. maintain rumen structure and motility. mixing feed with microbes. expelling gas. moving digesta to the reticulum

What stimulates rumen contractions

stretching, vagus nerve control, presence of feed and chewing activity, rumen pH and gas levels, and VFA concentration and nutrient balance

why are rumen contractions?

ensures feed is evenly exposed to microbes for fermentation. helps sort feed: small feed to the reticulum, large ones are regurgitated for re-chewing. prevents gas buildup by expelling it. moves partially digested feed toward the omasum and abomasum for further processing

How does newly ingested feed flow through the ruminant stomach?

Mouth-esophagus- Rumen and Reticulum- regurgitation- reticulum -omasum- abomasum- small intestine- large intestine

what is rumination

regurgitate partially digested feed from the rumen, rechew it, and reswallow it

what are the four steps of rumination

regurgitation, remasctication, resalivation, and rediglutition

factors that affect rumination time

feed particle size, fiber content, feed intake amount, rumen health &pH, animal species &size, and feeding management

development of the ruminant stomach- birth

the abomasum is the largest chamber. the rumen, reticulum, and omasum are very small and undeveloped

development of the ruminant stomach transition (3-8 weeks)

as the animal begins to nibble on solid feed, the rumen and reticulum begin to enlarge and develop papillae on the lining

development of the ruminant stomach -mature ruminant

the rumen becomes the largest compartment. the abomasum becomes smaller

what is the esophageal groove

is a muscular fold in the wall of the reticulum that forms a tube-like channel when the young animal nurses

What particle is “extracted” from macronutrients that drives ATP production in cells?

electrons

What is a redox reaction?

a chemical reaction involving the transfer of electrons between two substances

why redox reactions matter in cellular energy metabolism

they release energy from nutrients, they transfer energy viar carriers, they drive ATP production

What are the main electron carriers that participate in redox reactions in cellular energy metabolism?

NAD+/NADH, FAD/FADH2,

What is the difference between substrate level phosphorylation and oxidative phosphorylation?

substrate level does not require oxygen, occurs directly in metabolic pathways, produces less ATP per glucose than oxidative phosphorylation. Oxidative phosphorylation requires oxygen as the final electron acceptor

where does the citric acid cycle occur

mitochondiral matrix

where does the electron transport chain occur

inner mitochondrial membrane

What are the substrates and products of the citric acid cycle (per turn)?

substrates: Acetyl- CoA (2 Carbons) and Water. main products: 2CO2, 3NADH, FADH2, 1ATP

what does citrate synthase in the citric acid cycle do?

first step. 4C + Acetyl-CoA (2C) —- Citrate (6C) condensation reaction. forms citrate from oxaloacetate and acetyl-CoA