Functions of the Gastrointestinal Systems of animals (MOUTH + STOMACH) Flashcards
What is digestion?
breakdown of large insoluble food compounds into smaller water-soluble components so that they can be absorbed into the blood plasma.
What are the two types of digestion?
mechanical digestion
chemical digestion
What is the process called in mammals where food is chewed?
mastication
What is mechanical digestion?
- in mouth
- food is physically broken down
What is chemical digestion?
- gastrointestinal tract
- digestive enzymes
What is defecation?
release of feces through the anus.
What does the digestive systems of animals depend on?
- diet
- habitat
- other physiological characteristics
- more complex in omnivores
- most complex in herbivores
How is the digestion process controlled?
- autonomic nervous system
- hormonal control
- reflex mechanism
What types of nerves stimulate digestion?
parasympathetic nerves
What types of nerves inhibit digestion?
sympathetic nerves
What is the function of short reflexes?
- provide digestive tract with extensive self control
- stimulatory effects on the digestive processes
- inhibitory short reflexes are important for relaxation of GI sphincters
What is the function of long reflexes?
- originate within and outside the digestive tract
- involve long neural pathways between the central nervous system in the walls of the digestive tract.
What is the secretion of saliva regulated by?
autonomic nervous system
Explain the regulation of hunger.
What is the hunger center regulated by?
“hungry blood”- low in glucose, amino acids, etc.
empty stomach which irrigates gastric mucosa mechanocereptors
What is injection?
entry of food in the digestive system
mechanical and chemical digestion
mastication and mixing
absorbtion
nutrients are absorbed from the digestive system into the circulatory and lymphatic system
excretion
removal of undigested materials from the digestive tract through defecation
What are the functions of the digestive system?
- feed intake and mechaical crushing
- secretory
- motility
- breakdown of nutrients (hydrolysis)
- resporption
- exretion
- protection
- endocrinic
- analytical
What is peristasis?
wavelike motion
mixing
mixing motion
- oral cavity and stomach
- mechanical digestion
segmentation
- small intestine contractiona nd relaxing
What are the two parts of the digestive system?
- gastrointestinal tract
- accessory organs
the oral cavity
- mechanical processing (teeth, tongue, palatal surfaces)
- lubrication
- initiation of swallowing reflex
What is prehension?
- bringing food to the mouth
- mechanisms vary with behaviour and diet
What is mastication? What is it completed by? What muscle? What does it lead to?
- teeth, jaw, tongue, teeth
- striated muscle
- controlled voluntary
- reduces size of particles (chewing) + moistenes (mixing with saliva)
Explain salivary secretion. What is it secreted by? State the three types.
- saliva
- salivary glands
- 3 glands: parotid, mandibular, sublingual glands
What does the type of saliva depend on?
- quantity and composition of saliva varies between species (food consistency)
What are the functions of saliva?
- lubrication
- antibacterial effect
- enzymatic digestion
- pH regulation
- binding of tannins
- providing urea for protein synthesis in the forestomachs
- thermoregulation
How are saliva secretions regulated?
- neural control (via sympathetic and parasympathetic nervous systems)
- parasympathetic –> increase saliva secretions (Watery consistency)
- sympathetic –> small volume of highly viscous saliva
What does sympathetic stimulation result in?
- decreased production of saliva by acinar cells
- increased protein secretion
- decreased blood flow to glands
What does parasympathetic stimulation result in?
- acinar cells increase the secretion of saliva
- duct cells increase HCO3- secretion
- co-transmitters result in increased blood flow to the salivary glands
- contraction of myoepithelium to increase the rate of expulsion of saliva
swallowing
- ## voluntary action
What is the function of the pharynx?
Seperate the respiratory and digestive systems.
What is the esophagus?
- small muscle lines tube
- muscle cells –> spincters
- peristalsis (wave like contractions)
Explain the physiology of the stomach.
monogastric stomach: cats and dogs
- temporary food store
- digestion of food
-
chyme
mixture of feed and digestive secretions
glandular stomach
- cardiac
- fundic
- body
- pyloric
types of cells is the stomach
- chief cells: secrete pepsinogen
- parietal cells: secrete HCL and intrinsic factor (glycoprotein) (helps vit B12 absorption)
- mucin-rpoducing cells: secrete mucous and alkaline substances
- endocrine cells: gastrin (stimulated parietal cells), ECL cells (histamine - reduces production of HCL)
function of HCL
- lowers stomach ph
- PEPSINOGEN –> PEPSIN
- acidifies stomahc content
- degrades conective tissue and muscle tissue
- denaturation
- kills microorganisms
digestion enzymes
- amylase- carbohydrate digestion (resulting in disaccharides)
- pepsin- protein digestion (results in peptides)
- lipase- lipid digestion (results in fatty acids)
what are the phases
- cephalic
- gastric
- intestinal phase
cephalic phase
- sight, smell and taste food -> stimulate food digestion
gastric phase
- distention of stomach (stretch-receptors)
- chemoreceptors
intestinal phase
- release of hormones
- inhibit gastric function
- (sensory stetch receptors are stimulated)
rabit stomach
- always full
- monogastric
- no vomiting
avian stomach
- crop: moistened
- proventriculus: mixed with mucous and digestive juices
- gizzard: mashed and ground (mascular walls and gravel)
