ASCI243 - Digestive Systems and Digestive Physiology

What is classified as the digestive system?

The muscular tube from the mouth to the anus

What are the primary functions of the digestive system?

Prehension, mastication, absorption, and elimination

What is the definition of digestion?

The transformation of nutrients into compounds small enough to be absorbed and utilized as energy and tissue development and maintenance

What things are classified as nutrients?

Protein, minerals, CHO, vitamins, and fats

What is true of the digestive system in terms of endocrinology?

It plays a role in endocrine factors, such as regulation intake and metabolism

What are some examples of regulation hormones in the digestive system?

Leptin and NPPY

What does the digestive system do in terms of infections?

Protects against bacterial infection.

What is the function of the mouth?

Collecting, holding, grinding, and mixing

What is the function of the teeth?

Mastication and defense

What is the function of the tongue?

Taste, mastication, and grooming

What is true of the pharynx?

It is the common passageway for food and air

What are muscles in the pharynx responsible for?

The orderly direction of food/air

Where is the muscular tube?

Posterior of the pharynx to the stomach (i.e., posterior and anterior of the diaphragm)

What is the role of the cricopharyngeal?

Function as a caudal sphincter (not to be confused with a strict sphincter)

What type of GIT are humans?

Cucinovores

What are the three types of herbivores?

Post-gastric fermenter, non-ruminant foreguts, and pre-gastric ferment

What are carnivores?

Animals whose dietary requirements are primarily derived from animal tissue

Which accurately describes the carnivore?

Short GIT and low coefficient of fermentation when compared to herbivores

Which carnivore has the shortest GIT?

Cats

What is true of the teeth and amylase of carnivores?

They contain tightly-interdigitated teeth that have a lack of salivary amylase

What are the two types of carnivores?

Obligate and facultative

What are obligate carnivores?

Animals that must eat meat to survive

What are facultative carnivores?

Carnivores that can survive with limited meat (survive, not thrive)

What is the justification behind the status of dogs as carnivores?

They have tightly-interdigitated teeth, a lack of salivary amylase, a coefficient of fermentation that is similar to the of obligate carnivores, and an innate behavior that mimics obligate carnivores.

What is true of the giant panda?

They are carnivores

What is the enigma surrounding giant pandas?

They are classified as carnivores, but eat the diet of a herbivore with 99% of their diet being bamboo.

What is true of the bamboo diet of giant pandas?

They are required to spend 10-16 hr/day eating two varieties of bamboo

What accurately describes the ruminant stomach?

A single, modified stomach with three distinct voluminous diverticular

What accurately describes the non-ruminant stomach?

A single, simple stomach that is monogastric with hindgut fermentation

What are the three voluminous diverticula of the ruminant?

The ruminoreticulum, the omasum, and abomasum

Which is true of the ruminoreticulum?

The esophagus pumps directly into both the rumen and reticulum, but fibrous feed-stuff enter the rumen and larger particles + foreign objects go to the reticulum.

What is the sulcus ruminoreticularis?

An esophageal groove that acts as a muscular wall that, when contracted, directs milk directly to the reticulum

What are the two functions of the reticulum?

Transport liquid ingesta from the rumen to the omasum + sort large (foreign objects) into the ventral aspects

What does the reticulum do in terms of foreign objects?

Further breaks them down or permanently stores the,

What is true of the rumen?

It is an anaerobic fermentation chamber that is responsible for the breakdown of cellulose and hemicellulose.

What occurs in the rumen in terms of CHO?

They are fermented into VFAs before being sent to the reticulum

What is true of the omasum?

It is the primary site of absorption (i.e., H2O, VFA’s, electrolytes, and minerals) with some limited fermentation

What is the abomasum?

The glandular stomach, also known as the “true stomach”

What occurs in the abomasum?

Chemical digestion of dietary and bacterial proteins

What non-ruminants contain a single glandular stomach (SGS)?

Carnivores and omnivores

What modified non-ruminants are hindgut fermenters?

Equines

What is true of the equine stomach?

They have a single stomach with a non-GS section and a GS section

What is the role of the duodenum?

Connects the small intestine to the stomach

What does the duodenum introduce?

Enzymes from the gall bladder

What is true of the jejunum?

It is the site of primary absorption

What occurs in the Ileum?

The absorption of bile salts and any left-over nutrients occurs

What are the two primary sections of the large intestine?

The cecum and the colon

What are the three parts of the colon?

The ascending, transverse, and descending

What is true of the cecum in carnivores?

It is extremely small to nonexistent

What is true of the cecum in omnivores?

It is a small, “blind sac”

What occurs in the cecum of omnivores?

The absorption of fluids, enzymatic salts, and lubrication of waste

In herbivores, what is true of the cecum?

As postgastric fermenters, their cecum has a complex role in digestion with an enlarged site of fermentation (cellulose)

What are some examples of postgastric fermenters?

Equine, rabbits, rodents (insectivores), and koalas

What is true of the cecum on ruminants?

It has an unknown role, but it does act as a site of limited fermentation and a site of storage and transition.

What is true of the cecum in equines?

They have the largest and most complex cecum (~30 L)

What occurs in the cecum of equines?

Bacterial fermentation similar to ruminants with VFA’s being absorbed in the descending colon

What is coprophagy in terms of cecotropes?

Consumption of feces (i.e., consumption 1/day during morning or night)

What accurately describes the mammalian stomach?

It is a simple stomach with four functional compartments

What does the cardia stomach do?

Produces thick mucus and buffers for the protection of epithelial tissue

What is the glandular aspect of the cardia stomach?

The cardiac glands

What is the glandular aspect of the fundic stomach?

The oxytic glands

What is the function of the fundic stomach?

The production of gastric acid, proteolytic enzymes, hormones, and mucus

What are the glandular aspects of the pyloric stomach?

The pyloric glands

What is the function of the pyloric stomach?

Produce mucus and buffers with no acid or enzymes

What do G-Cells produce?

Gastrin

What initiates the release of gastrin?

The stretch of body or the stomach initiates the release of gastrin

What makes up the accessory glands?

Salivary glands, the pancreas, and the liver

What are the primary salivary glands?

The parotid, mandibular, and sublingual

What is the function of the pancreas?

Produce bicarbonate (HCO3) and digestive enzymes, like trypsin and chymotrypsin

What is the function of trypsin and chymotrypsin?

Protein breakdown

What is amylase directed at?

CHO’s

What is lipase directed at?

Lipids

What does the exocrine function account for in the pancreas?

95% of tissue

What is the endocrine function of the pancreas?

Glucose metabolism

What is Beta cells in terms of insulin?

Initiates storage of glucose into muscle and liver

What is alpha cells in terms of glucagon's?

Increase blood sugar (gluconeogenesis)

What is S cells in terms of somatostatin?

Inhibits GH Secretions

How many functions does the liver have?

500 essential tasks

What is the primary function of the liver?

Homeostasis

What are some additional functions of the liver?

Metabolic regulation, secretory, detoxification, and storage

What does the liver store?

A, D, E, K, and B12 Vitamins

What is vitamin K essential for?

The production of blood coagulants

What is glycerol required for?

Gluconeogenesis

What does the liver also produce?

Albumin and angiotensinogen

What is albumin?

The primary protein of blood serum — transportation of lipids

What is angiotensinogen?

A hormone that raises blood pressure in the presence of renin

What is angiotensinogen apart of?

The renin-angiostein-aldosterone axis controlled extracellular fluid volume

What is the liver apart of in terms of immune function?

The mononuclear phagocyte system

What do krupffer cells do?

Encase and destroy disease-causing agents within the liver, such as bacteria and toxins

What is true of the liver in terms of blood detoxification?

It involves bilirubin, hormones (estrogen and aldosterone), and toxins

What is phase 1 of liver detoxification?

Enzymatic modification (biotransformation)

What enzyme is involved in Phase 1 of liver detoxification?

Cytochrome P450 Family

What does Cytochrome P450 Family do?

Alters toxins to make them more H2O soluble

What is phase 2 of liver detoxification?

Conjugation

What occurs in Phase 2 of liver detoxification?

Modification of toxins to neutralize, easier to excrete (i.e., conjugation with other compounds)

What is oxidation?

A reaction that loses electrons

What is reduction?

A reaction that gains electrons

What accurately describes phase 1 of liver detoxification?

Modification of metabolites, toxins, and drugs to increase H2O solubility

What is the first phase of alcohol liver detoxification?

Ethanol (C2H5OH) is oxidized to acetaldehyde

What is the second phase of alcohol liver detoxification?

Acetaldehyde is oxidized to acetate