advance digestive physiology (part 1) by: a. riasi (phd in animal nutrition and physiology)...
TRANSCRIPT
AdvanceAdvance Digestive Digestive
PhysiologyPhysiology((part 1part 1))
By: A. Riasi (PhD in Animal Nutrition and Physiology)
Http://riasi.iut.ac.ir
Isfahan University of Technology
Development of digestive system
The properties of ruminant’s digestive tracts
Salivation
The receptors
The salivary glands
Control of salivation
The topics
Mastication and swallowing
Rumen and reticulum properties
Characteristics of the preruminant stomach
The wall structure
Development and control of forestomach motility
Blood circulation
Receptors
The topics
Rumination and its components
Attempts to control ruminoreticulum fermentation
Events associated with eructation
Absorption
Urea recycling
The role of thermodynamics in ruminant digestive
The topics
Omasum
Omasal motility
The properties of obomasum
Glands and secretions
Microscopic anatomy
Abomsal motility
The topics
Small intestine
Wall layers
Neuronal network
Blood circulation
Movements control
Transport systems in the epithelia
Entrogastric inhibitory reflex
The topics
Large intestine
Wall properties
Absorption
Motor activity of cecum
Evacuation contractions
Defecation
The topics
References Ruminant Physiology, by Sejrsen et al (2006)
Ruminant Physiology, by Cronje (2000)
Farm Animal Metabolism and Nutrition, by D’Mello
(2000)
Original and review papers
Advantages of pregastric fermentation
Make better use of alternative nutrients
Cellulose
NPN
Ability to detoxify some poisonous compounds
Oxalates, cyanide, alkaloids
Advantages of pregastric fermentation
More effective use of fermentation end products
Volatile fatty acids
Microbial protein
B vitamins
Decrease in handling undigested residues
In wild animals, it allows animals to eat and run
Disadvantages of pregastric fermentation
Fermentation is inefficient
Energy
• Loss Amount (% of total caloric value)
Methane 5-8
Heat of fermentation 5-6
Disadvantages of pregastric fermentation
Fermentation is inefficient
Protein
• Some ammonia resulting from microbial degradation will be
absorbed and excreted
• 20% of the nitrogen in microbes is in the form of nucleic
acids
Disadvantages of pregastric fermentation
Ruminants are susceptible to ketosis
Ruminants are susceptible to toxins produced
by rumen microbes Nitrates Nitrites
Urea Ammonia
Nonstructural carbohydrates Lactic acid
Tryptophan Methyl indole
Isoflavonoid estrogens Estrogen
Development of digestive systemDevelopment of digestive system
Common Duiker, Deer
Goats, Sheep, Moose
Cattle, Bison
Development of digestive systemDevelopment of digestive system
Common Duiker, Deer
Goats, Sheep, Moose
Cattle, Bison
Development of digestive systemDevelopment of digestive system
Common Duiker, Deer
Goats, Sheep, Moose
Cattle, Bison
Development of digestive systemDevelopment of digestive system
Common Duiker, Deer
Goats, Sheep, Moose
Cattle, Bison
The digestive system of animals has
different function:
Ingestion (eating)
Chewing (mastication)
Swallowing (deglutition)
Absorption of nutrients
Elimination of solid wastes (defecation)
The ruminant digestive tract
The wall of digestive tract as a hollow
organ consisting of several layers:
Mucosa,
Submucosa,
Muscularis externa and
Serosa/adventitia.
The ruminant digestive tract
The ruminant digestive tract
The ruminant digestive tract
The ruminant digestive tract
The functions of mucosa:
Secretion of enzymes, acid, mucin, hormones and
antibodies,
Absorption of the break down products of digestion,
water, vitamins and etc,
Barrier to prevent the entry of antigens, pathogenic
organisms, and immunologic protection.
The ruminant digestive tract
The digestive system of ruminant animals
includes the different parts:
Oral cavity
Esophagus
Multi-chambered stomach
Small intestine
Large Intestine
The ruminant digestive tract
Salivary glands and salivation
◦ Secretions contain:
Enzymes (amylase and lipase)
Water
Glycoproteins
Salivary gland and salivation
Salivary glands and salivation
◦Saliva has secretory IgA, lactoferrin and
lysozyme.
◦Saliva can serve a neutralizing function
Salivary gland and salivation
The salivary glands have different function
◦ Preparing enzymes
◦ Moistens and lubricates feed
◦ Water balance
◦ Bloat prevention
◦ Recycling of N and minerals including Na, P, and S
◦ Buffer secretion
Salivary gland and salivation
The architecture
◦Secretory units
Serous
Mucous
Salivary gland and salivation
◦Ducts
Intercalated
Striated intralobular
Interlobular
Main excretory duct
◦Myoepithelial cells
◦Lymphocytes and plasma cells
Salivary gland and salivation
Salivary gland and salivation
Salivary gland and salivation
In the left panel you see both serous and mucous secretory areas, in among the strands of skeletal muscle in the tongue. At right, a large serous gland is discharging via a duct (D) into the moat (M) around a vallate papilla.
Salivary gland and salivation
Different kinds of salivary galnds
Parotid
Mandibular
Sublingual
Some minor gland
Salivary gland and salivation
Salivary gland and salivation
Salivary flow
◦Saliva production occurring in 2 phases:
Primary secretion
Ductal secretion
◦The salivary ducts rely heavily on the
Na/K/2Cl cotransporter.
Salivary gland and salivation
Salivary flow
◦The degree of modification of saliva in the
ducts turns heavily on salivary flow rate. Fast rates result in a salivary product more like the
primary secretion.
Slow rates result in an increasingly hypotonic and
potassium rich saliva.
◦Effect of autonomic nervous system
Salivary gland and salivation
Salivary flow
◦ Ruminant produce a high daily output of saliva.
6 to 16 L/d in sheep
60 to 160 L/d in cattle
Salivary gland and salivation
Salivary glands Total salivary volumes (L d)
Characteristics Site of reflexogenic stimuli
Parotids
Inferior molars
Palatine, buccal, pharyngealSubmaxillary
Sublingual, labial
3-8
0.7-2
2-6
0.4-0.8
0.1
Serous, isotonic, strongly bufferedSerous, isotonic, strongly bufferedIsotonic, strongly buffered
Mucous, hypotonic, weakly bufferedVery mucous, hypotonic, weakly buffered
Mouth, esophagus, ruminoreticulumMouth, esophagus, ruminoreticulumMouth, esophagus, ruminoreticulumMouth during feeding, not cuddingMouth
Total volume 6-16
Salivary gland and salivation
Salivary flow◦The secretions from the parotid glands are:
Isotonic with blood plasma,
Have no significant amylase content,
Change their composition in response to salt
depletion,
Have a high alkalinity (pH 8.1)
Recycling the N and P
Salivary gland and salivation
Salivary flow
◦A 700 kg dairy cow fed a hay-grain diet will
secrete:
190 l saliva/day containing
30-80 gm total N
1100 gm NaHCO3
350 gm Na2HPO4
100 gm NaCl
Salivary gland and salivation
Control of salivary flow◦A basal level of parotid secretion occurs even
in the totally denervated.
◦Excitation of the secretory (acinar) cells by by
the parasympathetic nerve endings.
◦The increase in parotid blood flow does not
exactly parallel the increase in parotid
secretion.
Salivary gland and salivation
◦Salivary reflexs are integrated in salivary
centers located in the hindbrain.
◦The buccal mechanoreceptors located in or
near the tooth sockets have major effect.
Chewing of ingesta in cattle may increase salivary
secretion from 2 ml/min to 30 to 50 ml/min.
Salivary gland and salivation
◦The distension of the esophagus, reticulum,
reticuloomasal orifice, and ruminoreticular
◦Little increase is evoked by lightly stroking the
ruminoreticular epithelium.
◦Reflex increases in salivation may be inhibited
by concurrent stresses and excitement.
Salivary gland and salivation
◦ Some feeding factors may affect the saliva flow:
Dietary fiber concentration
Forage to grain ratio of the diet
Maturity of the forage
◦ Diet particle size
Grinding
Grain processing by-products
Diet moisture level
Salivary gland and salivation