MBS 217 Lecture 4 and 5 Flashcards
What does the digestive system anatomy consists of:
Digestive tract
Accessory organs
Regions
Accessory organs are also known as
Primarily glands
Functions of the digestive system
Ingestion: Introduction of food into stomach
Mastication: Chewing
Propulsion: Deglutition: Swallowing
: Peristalsis: Moves material through digestive tract
Mixing: Segmental contraction that occurs in small intestine
Secretion: Lubricate, liquefy, digest
Digestion: Mechanical and chemical
Absorption: Movement from tract into circulation or lymph
Elimination: Waste products removed from body
Structure of the lingual fenulum
The base of the frenulum contains a v shaped hump of tissue in the floor of the mouth, which houses a series of saliva gland ducts.
The two largest ducts are in the center just in front of the attachment of the lingual frenulum and are calledWharton’s ducts. They empty the submandibular submaxillary and sublingual glands
Functions of the salivary glands
- Prevents bacterial infection
– Lubrication
– Contains salivary amylase - Breaks down starch
Name the salivary glands
Parotid: Largest
– Submandibular
– Sublingual: Smallest
Structure of parotid glands
Parotid glands have mainly serous acini; producing large
amounts of salivary amylase; secretions drained by the
Stensen duct emptying at the vestibule at level of upper
molar.
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Structure of sublingual glands
Sublingual glands have mainly mucous acini; act as buffer
and lubricant; sublingual ducts (Rivinus ducts) open either
side of the lingual frenelum.
The sublingual gland is inferior to the mucosa of the floor
of the mouth and is anterior to the deep process of the
submandibular gland.
Structure of Submandibular glands
Submandibular glands have a mixture of mucous and
serous acini.
Secrete a mixture of buffers, glycoproteins (mucins) and
salivary amylase
Submandibular ducts (Whartons ducts) open on either side
of the lingual frenelum immediately posterior to the teeth
Composition of saliva
Salivary glands produce about 1.5 liters of saliva
daily
– 99% water
– 0.6 % electrolytes (Na, Cl, HCO 3 Buffers, glycoproteins, antibodies and waste products).
Function of salivary amylase
Salivary amylase (ptyalin) begins to break down
starch (inactivated in the stomach)
Function of Salivary lipase:
begins fat digestion, but has
minimal effect
Function of Glycoproteins (Mucins)
to lubricate the food for easier swallowing
Function of Lysozyme
Lysozyme to kill bacteria
Percentage of secretion of each gland
70% of saliva originate in the submandibular
salivary gland
– 25% parotid
– Remaining in the sublingual
What does saliva do in the mouth
Continuous level of saliva flushes oral surfaces
keeping clean
Prevent build upon of acids and bacterial action
pH of buffer in mouth
7
What controls oral bacteria (stress, radiation etc causes reduction and explosion of bacteria in oral cavity)
Antibodies IgA and Lysozyme which c
Control of salivary secretion
Autonomic nervous system
What are the secretion glands innervated by
sympathetic and parasympathetic nerves
Function of the villus
Blood supply in the villus which absorb the end products of digestion from the epithelial cells
Parasympathetic is stimulated by
trigeminal nerve or taste buds innervated by cranial nerve VII,
IX, X.
Function of Parasympathetic stimulation
speeds up secretion (feed and breed)
Pharynx
Nasopharynx
– Oropharynx: Transmits food normally
– Laryngopharynx: Transmits food normally
Esophagus
Transports food from pharynx to stomach
– Passes through esophageal hiatus (opening)
of diaphragm and ends at stomach
* Hiatal hernia
– Sphincters
* Upper
* Lower
Structure of the colon
- The lumen of the colon
- The mucus producing goblet cells
- Muscular walls to maintain peristalsis
Increase surface area of the Gut lumen
The inner intestine wall is folded which increases the available surface area by three times.
The villi are finger like projections into the lumen of the gut. These increase the available surface area by ten times.
Microvilli increases further
Function of the lacteals
The lacteals (green) that receive the lipoproteins before
transporting them to the circulatory system.
Function of the muscular walls
Muscular walls that maintain the movement of chyme by
peristalsis.
How does microvilli increase surface area
The cell membrane of the epithelial cells is folded into
microvilli. This increases the available surface area still
further
Histology of stomach
Layers
– Serosa or visceral peritoneum: Outermost
– Muscularis: Three layers
* Outer longitudinal
* Middle circular
* Inner oblique
– Submucosa
– Mucosa
* Rugae: Folds in stomach when empty
* Gastric pits: Openings for gastric glands
– Contain cells
* Surface mucous: Mucus
* Mucous neck: Mucus
* Parietal: Hydrochloric acid and
intrinsic factor
* Chief: Pepsinogen
* Endocrine: Regulatory hormones
Modifications of the small intestine
Circular folds or plicae circulares, villi, lacteal, microvilli
What are the types of cells of mucosa
Absorptive, goblet, granular, endocrine
What are the secretions of the small intestine
- Mucus
– Protects against digestive enzymes and stomach acids - Digestive enzymes
– Disaccharidases: Break down disaccharides to monosaccharides
– Peptidases: Hydrolyze peptide bonds
– Nucleases: Break down nucleic acids - Duodenal glands
– Stimulated by vagus nerve, secretin, chemical or tactile irritation of duodenal mucosa
Lobes of the liver
Major: Left and right
Minor: Caudate and quadrate
Ducts of the Liver
Common hepatic
Cystic
From gallbladder
Common bile
Joins pancreatic duct at
hepatopancreatic ampulla
Functions of the Liver
Bile production
– Salts emulsify fats, contain pigments as
bilirubin
Storage
– Glycogen, fat, vitamins, copper and iron
Nutrient interconversion
Detoxification
– Hepatocytes remove ammonia and convert to urea
Phagocytosis
– Kupffer cells phagocytize worn-out and dying
red and white blood cells, some bacteria
Synthesis
– Albumins, fibrinogen, globulins, heparin,
clotting factors
Gallbladder
Bile is stored and concentrated
What is the gallbladder stimulated by
Stimulated by cholecystokinin and vegal stimulation
Anatomy of the Pancreas - Endocrine
Pancreatic islets produce insulin and glucagon
Anatomy of the Pancreas - Exocrine
Acini produce digestive enzymes
Secretions of the pancreas
Pancreatic juice (exocrine)
* Trypsin
* Chymotrypsin
* Carboxypeptidase
* Pancreatic amylase
* Pancreatic lipases
* Enzymes that reduce DNA and ribonucleic acid
Structure of Large intestine
Cecum
– Blind sac, vermiform appendix attached
Colon
– Ascending, transverse, descending, sigmoid
Rectum
– Straight muscular tube
Anal canal
– Internal anal sphincter (smooth muscle)
– External anal sphincter (skeletal muscle)
– Hemorrhoids: Vein enlargement or inflammation
Secretions of Large Intestine
- Mucus provides protection
– Parasympathetic stimulation increases rate of goblet cell secretion - Pumps
– Exchange of bicarbonate ions for chloride ions
– Exchange of sodium ions for hydrogen ions - Bacterial actions produce gases called flatus
Movement in large intestine
Mass movements
– Common after meals
Local reflexes in enteric plexus
– Gastrocolic: Initiated by stomach
– Duodenocolic: Initiated by duodenum
Defecation reflex
– Distension of the rectal wall by feces
Defecation
– Usually accompanied by voluntary movements to expel feces through abdominal cavity pressure caused by inspiration
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