Chapter 11 Flashcards
Prehension
The first step of digestion.
The seizing and conveying of food to the mouth
Delivered to the mouth
Means of Prehension
Biped - Man & Apes; use our upper limbs, arms and hands
Quadrupeds - Domestic Animals; use mouth, teeth and lips, trunks etc.
Carnivores
Rely on teeth for ripping and tearing of flesh and meat.
Canine teeth, they have strong jaws and upper and lower molars
Cow - Ruminants
Mobile tongue; used to seize grass
Dental pad; no upper incisors but they do have lower incisors
Upper and lower molars for mastication
Sheep - ruminant
Mobile lip (cleft lip) - nibble more
Dental pad - no upper incisor
Graze closer than a cow and more selective than a cow
Horse - monogastrics
Mobile lips
Nibbles
Upper and lower incisors - can bite through food
Graze closer than a cow
Must chew thoroughly the first time. Cannot regurgitate
Horses teeth must be checked for proper alignment. Molars need to grind against one another
Avians
No lips
No teeth
Extreme diversity for seizing and conveying of food
Mastication
Vertical movements of the jaw which crush the food particles between teeth
Mastication for carnivores
Reduce the meal enough so that is can be swallowed
Rip, tear, swallow
Mastication for omnivores
Chew more than carnivores
Pigs - limited, don’t chew a lot
Avian - no teeth, no mastication
Humans - “slow down and chew your food”
Mastication for herbivores
Chew extensively
Need thorough mastication for their feed
Reduce particle size so it can move in GI tract
Mastication for herbivore ruminants
Chew extensively and then form a bolts, swallow and will go into the rumen, regurgitate and masticate more and will go back into rumen and ruminante. This process will continue
Typical dairy cow may chew about 42K times a day
Salivation
Produced by all animals
Secretion and mixing saliva with food
3 main paired salivary glands
Parotid - beneath ears
Submandibular - either side of jaw
Sublingual - under tongue
Amount of saliva produced varies with species, nature of diet, health of animal , etc.
Salivation in carnivores
Small amounts because they consume wet feed, about 200 ml/d
Salivation in omnivores
Varied, 1,500 ml/d
Depends on how much they chew
Salivation in herbivores
Horse about 40 liters
Cows about 60 liters
High producing dairy cows about 150 liters a day
Composition of saliva
Varies with species, diet, age, and health of animals
99% water
Mucin (mucus)
Electrolytes - Na & K
Salivary Amylase - enzyme that breaks down starch
Present in - man, apes, pigs, rats, some Avians
Not present in - cattle, dogs, cats or horses
Functions of Saliva
Lubrication of food
Acts as a solvent - dissolved food into solution allows food to mid with taste buds
Cleans oral cavity - inhibits growth of bacteria
Washes dental cavity
Buffer for NaCO3 in ruminants and providing nitrogen and phosphorus for fermentation in ruminants
Swallowing or Deglutition
Reflex of passing anything from the mouth through the esophagus to the stomach
Neural reflex:
Voluntary - first 1/3 of the process and involuntary - last 2/3 of process
Steps in Deglutition
- Neural reflex
- voluntary
- involuntary - Bolus of food moves down via peristaltic wave
- At the end of the esophagus there is the cardiac sphincter - does not allow reflux up and helps prevent committing. Ruminants do not have a cardiac sphincter.
Fundic or cardiac region
Upper section of the stomach
Secretes mucus and HCL
Body or proper gastric
Middle part of the stomach
Secretes HCL and Pepsinogen
Pyloric
Bottom part of the stomach
Secretes mucus and pepsinogen
Gastric Pits
Neck cells - top; produce mucus
Parietal cells - middle; HCL (we don’t want it active) produces through carbon anhydride
Chief cells - bottom; pepsinogen
HCL is not produced until it’s in the lumen
Stomach
Pigs, humans, dogs, (monogastrics) - glandular stomach
Chicken - proventriculus
Cows, sheep, ruminants - abomasum
All three types of digestion are at work- mechanical, chemical and enzymaticp
Mechanical digestion in the stomach
Muscular contractions that churn the digesta
Mixes the digesta with enzymes and chemicals
Chemical digestion in stomach
Gastric glands - parietal cells produces HCL
HCL unfolds proteins - exposes the proteins to enzymes. Activates enzymes in the stomach. Optimal pH (2-2.5) pepsin works best
Helps destroy bacteria - except food borne illnesses
Enzymatic digestion in the stomach
For the most part occurs by pepsin which is a protease. Proteases work on proteins, hydrolysis proteins
Pepsin producers by Chief cells, cleaves protein and makes shorter chain lengths.
Rennin - acts on milk protein (young)
Functions of stomach
Storage - stores for a period of time
Metering - meters or limits movement of digesta into Intestines
What keeps the stomach from digesting itself?
Mucin - secretes by neck cells and provides protection or coating
HCL is diluted in the stomach by saliva and digestion - food and saliva helps to buffer
Urease - enzyme that breaks down urea - acts as a buffer as well
Enzyme is secretes in an inactive form (zymogen). Only active in lumen if stomach
Small intestine
Divided into 3 parts
Duodenum
Jejunum
Ileum
Duodenum
First segment of SI Extends from pyloric sphincter to jejunum
Primary site of digestion
Jejunum
Second segment of SI
Extends from duodenum to ileum
Primary site for absorption
Ileum (terminal ileum)
Last segment of SI - smallest part
Extends from jejunum to large intestine
Secondary site of absorption
Bile
Made in the liver and stored in the gall bladder
Functions in two ways:
Detergent action - solubilizes fat
Forms complex with fatty acids
Secreted into duodenum
Pancreatic juice
Secretion from pancreas that contains very potent digestive enzymes
Secreted into duodenum
Main enzymes are Trypsin and Chymotrypsin - digestion Carboxypeptidase - digestion Pancreatic lipase - fat Amylase - starch
Contains buffers - HCO3 & NaCO3 - both neutralize acidic pH
Duodenal juice
Secreted by brush border
Contains enzymes secreted by intestinal mucosa
Large Intestine
The contents of the LI are not sterile - bacteria, Protozoa, fungi
Digestion is limited by mco
Absorption is limited - VFA, water and electrolyte
LI - Monogastric Herbivores
Horse, rabbit, guinea pig and elephant - extensive cecum and colon - provide good environment for mco
The LI of adult horses are comparable in size to the rumen in ruminants
LI and Ceca in monograstrics herbivores
Similar to fermentation in rumen but not as efficient
Because most of nutrient content is removed by the SI and past the site of primary absorption
Corophagy
Feeding on excrement
Rabbits and other species practice.
Two types of feces
Pellet type
Soft feces
Contains B vitamins and MCO protein
Defecation
Discharge of excrements from rectum it cloaca
Contents of decal material - Water Undigested feed Residues of digestive enzymes Sloughed cells Bacteria
Urination
Components of urine - Water Minerals - Cl, K, P, Na Nitrogen compounds - Urea - animals (livestock) Uric acid - birds Ammonia Will also include electrolytes Glucose and small carbohydrates
Substances found in urine
Should generally be considered waste produces if metabolism rather than digestion
