The Digest sys Flashcards
(25 cards)
Organs of the digestive system fall into 2 categories
- Alimentary canal(GI tract)
- Accessory digestive organs: supporting structures to the GI tract
True or False
The GI tract measures about 5m long in a living person, but about 9m in a cadaver
True because there is a loss in muscle tone after death
The functions of the digestive system
- selective food intake: ingestion
- breakdown of food; chemical and mechanical digestion
- absorption
- consolidation and elimination of indigestible remains: defaction
Mechanical vs chemical digestion
Mechanical: the physical breakdown of food
- exposes more food surface to the action of digestive enzymes
Chemical: the hydrolysis of macromolecules into monomers
- polysaccharides into monosaccharides(glucose, galactose, fructose)
- proteins into amino acids
- fats into fatty acids and glyercol
-nucleic acids into nucleotides
The Peritoneum
Is the largest serous membrane of the body
- the visceral layer adheres to most organs of the abdominal cavity
- the parietal layer attaches to the abdominal cavity wall
The organs of the peritoneum
Intraperitoneal(peritoneal) organs:
Organs that are located within the peritoneum
Retro peritoneal organs:
Organs located outside it posterior to it
Examples:
Duodenum, pancreas, kidneys, adrenal garlands and ureter
Some parts of the peritoneum
Form large folds called the omens and mesentery
The omenta
contains adipose tissue used for protection, insulation, and energy storage, and milky spots of macrophage for immune surveillance.
What is the greater omentum attached to?
• the stomach and transverse colon, and it folds over to cover the small intestine.
What is the lesser omentum attached to? the liver and stomach.
The mesentery
suspends the small intestine and loosely holds them in place.
What is the purpose of the mesentery?
• anchor the intestine in place, while still allowing some movement
• conduits blood vessels, nerves and lymphatic vessels
The GI tract consists of 4 basic walls
- The mucosa
- The submucosa
- the muscular is
- the serosa
The conposition of each layer varies from region to region
Interaction of the gastrointestinal tract
The GI tract is regulated by neural and hormonal inputs
Which branch of the nervous system does the GI tract receive signals from?
- The autonomic nervous system
- entreric nervous system
Hormones from cells in the stomach and small intestines e stimulate target cells in the same or different organs to secrete or contract
The enteric nervous system
Has 2 nerve plexuses: the submucosal and myentric nerve plexuses
- respond to stimuli in the GI tract lumen
- form short reflex loops with sensory neurons, interneurons and motor neurons
- acts indecently from the CNS
What are some examples of stimuli in the Gl tract lumen that regulate Gl motility and secretions?
- stretch
• changes in osmolarity and pH
• presence of substrate and end products of digestion
The autonomic nervous system
Regulates ENS reflexes
- parasympathetic nerves increase GI secretion and motility(rest and digest)
- sympathetic nerves decrease them
In the gut, long reflexes have an advantage over short reflexes in that
Long reflective pathways can be stimulated by substances outside of the GI tract
The tongue
contains interlacing bundles of skeletal muscles anchored posteriorly by the lingual frenulum.
What are the functions of the tongue?
• mixes food with saliva to form food bolus
• initiates swallowing by pushing bolus into the pharynx
• sense of taste
• facilitates speech
Teeth
Types:
Incisors:cut
Caines: tear and pierce
Premolar and molar: grind and crush
Teeth are important in mastication
The dental formula for an adult’s 2-1-2-3. What does the one stand for?
The canine tooth
Salivary glands
There are 3 groups:
- parotid: near the ear
- submandibular: below the lower jaw
- sublingual: below the tongue
Saliva
is a hypotonic mixture of enzymes, ions, mucus and water
- pH: acidic (6.75-7.00)
What are the functions of these components of saliva?
• water (97-99.5% of saliva): moistens, softens, and dissolves food.
• lysozyme: enzyme that kills bacteria.
• immunoglobulin A: antibacterial antibody.
• lingual lipase: enzyme that begins fat digestion in the mouth.
What is not a true statement about saliva
It contains acids which aid in chemical digestion
The esophagus
is a muscular tube guarded by the upper and lower esophageal sphincters (UES and LES).
The esophageal hiatus: where the esophagus passes through which connects to the stomach at the cardiac orifice (named for its proximity to the heart)
Modifications of the esophagus
- the submuscosa glands secrete mucus to aid in bolus movement
- muscularis externa contain skeletal muscle superiority, mixed in the middle and smooth muscles inferiorly
