Physio exam 1

I wanna kill knowt still hate this system

Mastication

Mastication

• Grinding and shearing actions of the teeth

• “cud chewing” is regurgitation of ingesta from the reticulum

  • followed by re-mastication and re-swallowing

Prehension in horses

lips

• stitch eating apples

Prehension in dogs and cats

Teeth

Prehension in ruminants

tongue

Prehension in sheep/goats

The tongue, incisor and lips

Prehension in pigs

The tongue, incisor, lips and propulsive movement of the head

Hypsodent teeth

• The teeth emerge from the gums at continuous rate as the animal ages

  • horse, cattle, sheep, goat, and other ruminants

Brachydont teeth

• Teeth wear and are not replaced

• Molars are covered entirely on the occlusal surface by the enamel

  • dog, cat, and human

Primary peristalsis

• continuation of the peristaltic waves that begins in the pharynx and spreads into the esophagus

• During pharyngeal stage of swallowing

  • Stimulated by swallowing

Secondary peristalsis

• Generated within the esophageal musculature by distension of the esophagus by the retained food

  • Stimulated by food (bolus) in the esophagus

Anatomical divisions of the stomach

• Cardia

• Fundus

  • MAIN portion of stomach

  • collects digestive gases

• Corpus

  • body

  • the body secretes pepsinogen and hydrochloric acid

• Pylorus “ the gate keeper “

  • includes pyloric antrum

  • mucus, gastrin and pepsinogen secretion

Layers that make up the stomachs mass

• Inner lining mucosa

• Submucosa

• Muscularis

• Adventitia

Three glandular regions in non ruminant stomachs

• Cardiac: cardiac glands

  • lower esophageal

• Fundus: gastric gland proper

  • orad region of stomach

• Pyloric: pyloric glands

The intrinsic nervous system: extramural plexus

• Independent from CNS

  • brain and spinal cord

• GI movements

  • Autonomic

• PSNS system increases(excitatory) GIT activity

  • Acetylcholine

• Extrinsic component consists of the sympathetic and

  parasympathetic branches

• Intrinsic is the enteric nervous system that is contained within the

  submucosal and myenteric plexuses

• SNS system has a net inhibiting effect

  • Norepinephrine

• 1st plexus located in the submucosa

• 2nd plexus between the longitudinal and circular muscles layers

Anatomic innervation of GIT

• Parasympathetic system increases activity

  • Acetylcholine

• Sympathetic system inhibits activity

  • Norepinephrine

The parasympathetic to the GIT

• Vagus nerve: motor and sensory fibers

  • supply to ALL regions of the ruminant stomach is by the dorsal vagal trunk

• Sensory fibers: monitor gut condition

• Motor fibers: boost digestive activity via intrinsic nervous system

Phasic contractions

• periodic contractions and relaxations

• occur in esophagus, antrum of stomach, and small intestne

Tonic contractions

• Constant contraction without regular relaxation

  • Occurs: in lower esophageal cardiac sphincter, orad region of the stomach (upper-fundus and proximal body), iliocecal sphincter, and internal anal sphincter

Stomach and hunger contractions in monogastric

• Adaptive relaxation

  • Reflex in which the fundus of the stomach dilates in response to small increases in intragastric pressure

  • vasoactive intestinal peptide (VIP)

• Peristaltic contraction

  • Wave-like muscle contractions

  • esophagus where strong wave-like motions of the smooth muscle move food to the stomach

  • Antiperistalsis: contractions of the intestine that force the contents in the opposite direction

• Terminal Antral Contraction

  • Closure of terminal sphincter facilitates mixing of material in the stomach to form chyme

Glossopharyngeal Nerve (CN IX)

• sensory input for the posterior part of the tongue and throat

  • Conrols: taste

• Glossopharyngeal Nerve is responsible

  • caudal 1/3 part of the tongue

Vagus Nerve (CN X)

• responsible for swallowing and enzymatic digestive organs

• parasypathetic (only one)

• both efferent & afferent

• Vago-vagal reflexes: controls contraction of the gastrointestinal muscle layers in response to distension of the tract by food

• Salivary

  • SNS and PSNS

Facial Nerve (CN VII)

• responsible for mastication and salivary glands' function

  • Taste buds are innervated by

  • Taste: controlled by rostral 2/3 of the tounge

Trigeminal Nerve (CN V)

• responsible for the sensory input and motor control of the muscles involved in chewing

  • Sensory and motor innervation mandibular branch

  • Controls: Temperature, touch and pain (Rostral 2/3) of the tongue

Slow waves depolarization phase

• Cyclic opening of Ca2+ channels

• Inward Ca2+ current

  • Cell membrane of ICCs are permeable to Na+ and Ca2+

  • easily depolarized

• Smooth muscle

Outer longitudinal muscularis externa depolarization and contraction

• reduce segment length

• Pendular: periodic contractions and relaxations of the longitudinal muscles of the intestinal wall

  • Prevents segmentation: prevents constipation

Slow waves repolarization phase

• Cyclic opening of K+ channels

• Outward K+ current

  • Smooth muscle

Inner circular muscularis externa depolarization and contraction

• reduce segment diameter

General GIT motility

• Unitary smooth muscle with electrical coupling via gap junctions.

• Exceptions: Pharynx, upper 1/3 esophagus, and external anal sphincter (striated muscle or skeletal)

Flavors detected by the tongue

• salty, sour, sweet, bitter, and umami tastes

Control of gastric emptying

• Duodenum stimulation by Cholecystokinin CCK release

  • mainly in lipids and proteins; suppressing gastrin

  • decreasing gastric emptying; and causing gallbladder contraction

• The vagovagal reflex controls the contraction of GI

  • in response to distension of the tract by food

• Local enterogastric reflexes (vomiting)

• Hormones

Inhibition of emptying of stomach contents into the small intestine

• duodenal acidic pH, distension, and hypertonicity

• sympathetic stimulation

• pain

• increased gastric chyme osmolarity

Small intestine segments

• Duodenum

• Jejunum

• Ileum

Small intestinal mucosa

• Crypts of Lieberkuhn

  • Goblet cells: glands of the intestinal mucos

• Plicae circulares

  • numerous folds of mucous membrane

  • folds of Kerckring

• Villi

  • microvilli

Structures of the small intestine

• The inner wall is covered by plicae circulare

• Major duodenal papilla (papilla of Vater): dilated junction of the pancreatic duct and the bile duct (ampulla of Vater) enter the duodenum

• Plicae circulare are covered in villi and microvilli

  • absorption

• Nutrients are circulated blood capillaries and lacteals or lymph channels

• Brunner’s glands: mucus glands normally found in the mucosa and submucosa of the duodenum

  • secrete mucus with an alkaline pH, which serves to neutralize chyme from the stomach

Law of the small intestine

• Maintenance of intestinal Peristalsis is only in the direction of the large intestine

  • Not towards the stomach

Mucosa Cell

secretes mucus

Three stages of deglutition

• Oral/voluntary stage

  • CN VII (Facial n.) & CN IX (Glossopharyngeal n.)

• Pharyngeal stage

  • Opening of the cranial esophageal muscle

  • max. pharyngeal pressure has been developed

• Esophageal stage

  • Contraction and relaxation of muscles

    • musculature generates peristaltic movements

Oral/Voluntary Stage

• Initial eating and bolus formation.

• Increased saliva production.

• Involves tongue motor coordination.

• CN VII (Facial n.) & CN IX (Glossopharyngeal n.)

Pharyngeal Stage

• Closure of nasopharynx and oropharynx.

• Opening of the cranial esophageal muscle

• Increased pressure in the throat.

  • Stimulated by swallowing

• Depression of the esophageal sphincter.

Esophageal Stage

• Esophageal sphincter opens to allow food passage

• Contraction and relaxation of muscles

Ileum

• Communicates with the cecum: Ileocecal sphincter or valve

• Gastro-ileac reflex: initiated by stomach affecting the ileum

  • Aboral movement

  • supporting gastric emptying

  • POSITIVE reflex

• Ileogastric reflex: initiated by ileum affecting the stomach

  • Oral movement

  • inhibiting gastric emptying

  • NEGATIVE reflex

The large intestine

• Water, ion, fatty acids, vitamins, and electrolyte absorption

• Major ion absorptive site

• Vat for indigestible materials

• Site for fatty acid absorption

  • (microbial fatty acids in the LI of horses and pigs

• Microbial fermentation

  • Especially of cellulose and hemicelluloses in herbivores and omnivores

• Volatile fatty acid production

• Ammonia production

  • from urea

• Site for vitamin production and absorption

  • vit. K, B12, thiamine, riboflavin, biotin, and folic acid

Endopeptidases

• attack peptide linkages involving specific amino acids in the interior of a polypeptide.

Junctional communication of the large intestine

• Ileocecal junction

• Ileocecocolic junction

• Rectoanal junction

Gastric juice functions

• Hydrochloric acid (HCl)

• Solubility of non-water soluble food

• Necessary for activation of pepsin

  • conversion of pepsinogen to pepsin

• Disinfectant

• Regulatory function: Stimulates duodenal cholecystokinin (CCK) secretion

  • hormone that regulates the release of bile and pancreatic juice

• 60-75% of ingesta fermented by microbes BEFORE exposure to gastric juices

Gastrin

• lower stomach, upper small intestine, and pancreas

• stimulates gastric secretion and gastric motility

• enhancing gastric mucosal growth

• secretion of hydrochloric acid (HCl) into the stomach

Villikinin

• Stimulates motility of intestinal villi

• aids in the transport of lymphatic fluid into the lymphatic ducts

Enterogastrone

• decreases gastric emptying and mobility of the stomach

Motilin

• Gastric mucosa

• Stimulates gastric motor activity

• gastric emptying

Pepsin in the presence of hydrochloric acid

conversion of pepsinogen, to pepsin

Gastric inhibitory peptide

It has enterogastrone-like activity

Enterocrinine

• stimulates intestinal secretion

  • secretion of large quantities of alkaline mucus

Exopeptidases

• Remove end single amino and carboxyl groups

• occurs after luminar digestion

• converted to free amino acids by amino-peptidases

Ribonuclease

• nuclease

• catalyzes the degradation of RNA into smaller components

The enzymes contained in pancreatic juice

• Elastase: catalyzes cleavage of carboxyl groups present on small hydrophobic amino acids

  • such as glycine, alanine, and valine.

  • breakdown of elastin

• Colipase: counteracts the neutralizing effects of bile salts (when in high concentration) on pancreatic lipase

  • procolipase inactive form

• Are capable of digesting all three major types of food classes

  • proteins, carbohydrates, and fats

Gall bladder not found in

Horses and Rats

Secretin

• Upper small intestine

• secretion of bicarbonate and water from pancreas.

• It inhibits gastric secretion and motility

• enhance the secretory potential of the intestinal secretory cells

• Stimulates ductal cells

  • deliver enzymes produced by pancreatic acinar cells into the duodenum

Gastric secretion during a meal can be divided into three phases

• Cephalic phase

  • Oral cavity: before food enters the stomach

• Gastric phase

  • Stomach: induced by vasovagal reflexes

  • stomach to brain

• Intestinal phase

  • Intestine: presence of food in duodenum

Pancreases

• large compound gland

• both exocrine and endocrine organ

  • parallel and beneath the stomach.

• secretes digestive enzymes and lots of sodium bicarbonates

Types of bile salts

• Cholic acid

  • Faurocholic & Glycocholic

• Deoxycholic acid

  • deoxycholic, chenodeoxycholic, and lithocholicacids

Vasoactive intestinal peptide (VIP)

• Duodenum

• Gastric receptive relaxation

• regulates smooth muscle activity, blood flow in the gastrointestinal tract

Cholecystokinin (CCK)

• Upper portion small intestine

• It stimulates pancreatic secretion

• Promots emptying of the gall bladder

  • hormone that regulates the release of bile and pancreatic juice

Pancreatic Proteolytc Enzymes

• Split proteins into small peptides or amino acids:

  • Trypsin: activated into the mature form by enterokinase

  • chymotrypsin

    • important digestive enzymes secreted by the pancreas as the inactive enzyme precursors trypsinogen and chymotrypsinogen

  • carboxypeptidase: are zinc-containing exopeptidases that remove single amino acids from the carboxyl end of oligopeptides

Carboxypeptidases

• Zinc-containing exopeptidases

• remove amino acids from oligopeptides

• Digestion of dietary proteins by pepsin

  • trypsin and chymotrypsin

Bile

• secrete by the bile secreting hepatocytes (liver cells)

• transported through the bile cananiculi into the bile terminal duct

• contains no digestive enzyme

• Bile salts have digestive relevance

• CCK regulates bile release

Bile salts

• emulsification of fat.

• exposes the fat molecules to lipase for maximum contact and digestion

• fats are reabsorbed by the ileum

• sodium bicarbonate keeps bile salts in solution within the bile.

• act on fats but most of them are reabsorbed by the ileum and then re-secreted by the liver

Bile pigment

• called bilirubin, yellow in color

• transported in blood

  • bound to albumin (unconjugated bilirubin)

• In the liver

  • incorporated in bile (conjugated bilirubin)

Bile is secreted continually by

• The liver

  • stored in the gallbladder

Rate of bile secretion is controlled by

• The concentration of circulating bile salt.

• Neural mechanism

• Hormonal mechanism

• Rate of blood flow

• secreted continuously by the liver rather than intermittently as in the case of most other gastrointestinal secretions

biliary reflex

• duodenogastric reflux

  • Causes painful heartburn, nausea, and vomiting and inexplicable weight loss

secreations of the small intestine

• Papilla of vater

  • is the point where the dilated junction of the pancreatic duct and the bile duct

• Brunner's glands

  • branched tubular mucus glands normally found in the mucosa and submucosa of the duodenum.

  • These glands secrete mucus with an alkaline pH

• Goblet cells

Digestive enzymes of the small intestines

• Peptidases

• Sucrase, maltase, isomaltase, and lactase

• Lipase

• Secretin and cholecystokinin (CCK) enhance secretory potential of the intestinal secretory cells

Large intestinal functions

• Volatile fatty acid: the large intestines

• Urea: converted to ammonia in the large intestine

  • Vitamin K, Vitamin B12, thiamin, riboflavin, biotin and folic acid formed and absorbed in the large intestine

The tongue

• Hypoglossal controls movement

• Temperature, touch, and pain is done via the trigeminal nerve (rostral 2/3rd)

• Sensation of taste is via facial (rostral 2/3rd) and glossopharyngeal (caudal 1/3rd) nerves controlled by their lingual branches

• Have various types of papillae with taste buds

Small intestinal motility

• Villous movement

  • enhances absorption (under the control of the muscularis layer

• Segmentation movement (circular muscle)

  • No movement helps to retain food for a certain amount of time to aid with digestion

• Peristaltic movement.

  • Aboral movement

• Anti-peristaltic movement

  • Oral movement

  • Nausea, reflux, and vomiting

Large intestinal motility

• Adaptive relaxation

  • accommodation of material d/t relaxation of muscles

• Antidromic (retrograde)

  • peristaltic waves

• Haustrations

  • of colon are the small pouches caused by sacculation

  • which give the colon its segmented appearance.

  • The taenia coli runs the length of the LI

  • High degree of haustrations is observed in animal that defecate palleted-shaped feces

• Pendular

  • periodic contractions and relaxations of the longitudinal muscles

  • Prevents segmentation, constipation

Phases of Digestion

• Luminal phase

  • lumen of the digestive tract

  • secreted enzymes and acid (initial hydrolysis of food)

  • Inadequate mixing of nutrients, bile, and pancreatic enzymes, also causes impaired hydrolysis

  • Failure to convert a proenzyme to its active form, cause maldigestion and malabsorption

• Membranous phase

  • Conducted by enzymes attached to membranes of enterocytes

  • Partial breakdown of food material

Absorption

• End of product of digestion blood capillaries or lymphatics of the villi

Transportation of absorbed Material

• Materials absorbed into the capillaries are carried to the mesenteric veins and the portal veins

The opening of the biliary and the pancreatic duct into duodenum varies in different animals

• Cow and pig: the bile and pancreatic duct open into the duodenum separately

• Goat and sheep: the duct systems join prior to arrival at the duodenum

• Horse, cat, and dog: common pancreatic bile duct

Deoxyribonuclease

• Enzymes degrade DNA via phosphodiester backbone hydrolysis

• Cleaves single or double-stranded DNA

• requiring metal ions

Villi

• Surface epithelial projections for absorption

• The central vein carries waste and products

• Central lymphatic responsible for absorbing dietary fats and fat-soluble vitamins

Elastase

• Serine protease from the pancreas

• Breakdown of elastin

• catalyzes cleavage of carboxyl groups present on small hydrophobic amino acids

  • such as glycine, alanine, and valine

Constipation

• Delayed peristalsis

  • infrequent and painful defecation

• Reduced large intestine motility leads to constipation

• Can be relieved by fiber which boosts fecal bulk

  • stimulating colon motility

GI hormones

• Mostly peptide hormones.

• Paracrine hormones come from intestinal lamina propria cells

• Intestinal endocrine hormones from specialized epithelial cells.

• Bind to specific receptors and create second messengers.

  • Secretin, gastrin, CCK, gastric inhibitory polypeptide and motilin

Biliary secretions and hepatic system

• Hepatocytes synthesize bile and secrete it into canaliculi

• Canaliculi combine into smaller bile ducts

• Aids in intestinal digestion and an excretory organ for the elimination of by-products

• Ducts merge to form the main hepatic duct

  • then exiting the liver

Metabolic aspects of digestion

• Chemical digestion by enzymes: hydrolysis

• Glycosidic linkages: carbohydrates

• Peptide bonds: proteins

• Ester bonds: fats

• Phosphodiester bonds: nucleic acids

Lipid digestion

• Initiated by pancreatic enzymes like lipase.

• Act at the oil-water interface of the emulsion particles releasing a β-monoglyceride (beta) and long-chain free fatty acids from the dietary triglyceride.

• Chylomicrons: produced in enterocytes from dietary lipids

  • transport dietary lipids, cholesterol absorbed by intestinal epithelia

Carbohydrate Digestion

• Salivary amylase:

  • absent in carnivores

Monogastric digestion

• Three glandular regions of the stomach

• Gastric juices: flow through gastric pits on the gastric mucosa

• The glands proper in the submucosa

Parental cells

• HCL

• Intrinsic factor

• Found: glands within the fundus and body of the stomach

• largest cells

• responsible for gastric acid secretion, which aids in the digestion of food, absorption of minerals, and control of harmful bacteria.

G cells

• synthesis and secretion of gastrin

• increases gastric contraction and emptying

• Found in the pyloric antrum

  • in the duodenum and the pancreas

Principles of GIT Slow waves

• Smooth muscle

• Origin occurs at interstitial cells of Cajal

  • spontaneous

• duodenum: 12 slow waves per minute

• stomach: 3 slow waves per minute

• ileum: 8-9 slow waves per minute

Chief cells

• produce pepsinogen and hydrochloric acid

• gastric lipase

  • that cleave the proteins into smaller pieces

• Found in the fundic stomach

Gastric intrinsic factor and anemia

• Intrinsic factor is secreted: parietal cells.

• Achlorhydria: absence of hydrochloric acid

• Pernicious anaemia: Vitimin B12 deficiency

• Control of parietal cell acid secretion

• Histamine (H2 receptors)

• Gastrin flow through blood to act on gastrin receptors

• Vagus nerve (Ach via muscarinic receptors)

Functions of pancreatic enzymes

• Trypsin and chymotrypsin: inactive enzyme

• Trypsinogen is activated: by enterokinase.

  • trypsin activates itself and converts chymotrypsinogen to its active form chymotrypsin

• Proteins: cleaved in the stomach under acidic pH conditions by pepsin into peptide fragments.

• small intestine: cleaved under alkaline conditions into oligopeptides and amino acids

• optimum pH range: pH 7 and pH 8

Enterohepatic circulation of bile

• Duodenum: stimulates CCK secretion

• Sphincter of Oddi relaxes

  • gallbladder contracts

• Bile forced into duodenum

  • aids fat digestion

• Ileum: bile acid absorption

  • recirculated to liver

• Liver reabsorbs

  • re-secreted into bile for more formation.

Large intestine secretion

• No villi

• No digestive-enzyme glands

• Large intestine lacks

  • ascorbic acid, vitamin B12, choline due to bacteria

• Alkaline secretion

  • bicarbonate and mucus

• Large intestine secretes water and electrolytes.

Absorption of water and electrolytes

• Passive diffusion: potassium, Bicarbonate and chloride ions, Fructose, Pentoses (mannose, xylose, arabinose)

• Calcium ions: active/passive

• Active transport: iron, calcium, sodium, Glucose and galactose(sodium-dependente), proteins (sodium-dependent)

calcium absorption regulated by factors like

• Facilitated by lactose and protein

  • Lactose acts as a prebiotic

  • Protein increases HCl secretion

    • thus increasing solubility and increased absorption

• Inhibited by insoluble salts

  • phosphates and oxalates

• Interfered with by high-fat concentrations.