Digestive System Lecture Flashcards
Alimentary Canal
(Gastrointestinal tract, GI)
A hollow tube that runs from mouth to anus. Maintaining homeostasis of the lumen in this canal is important.
Pathway of Alimentary Canal
oral cavity, pharynx, esophagus, stomach, small intestine, large intestine –> anus
Accessory Digestive Organs
Organs that mostly sit outside of alimentary canal and send substances to the lumen.
Examples: tongue, teeth, salivary glands, liver, gallbladder, and pancreas.
Ingestion
Taking food in at the oral cavity
Propulsion
Ability to move substances through the alimentary canal
Examples: swallowing and peristalsis
Mechanical Digestion
Using physical force to break apart large structures to smaller ones
Examples: mastication, segmentation, and churning
Churning
Using force to twist food inside the stomach into smaller substances
Chemical Digestion
Breaking chemical bonds in the foods that we eat using enzymes.
Purpose: to get to smallest absorbable form
Absorption
Allow nutrients and h2o from lumen in the alimentary canal to be absorbed by our blood/ lymphatics
Defecation
Ability to get rid of all indigestible and non-absorbable substances
Peristalsis
Type of propulsion; as smooth muscle in alimentary canal constricts, foodstuff gets moved
Segementation
Type of mechanical digestion; contracts smooth muscle nonadjacent walls in lumen so foodstuffs can collide and break apart
Layers of Alimentary Canal
-Mucosa (innermost)»_space;epithelium, lamina propia, & muscularis mucosae
-Submucosa
-Muscularis externa
-Serosa or adventitia (outermost)
Epithelium
In mucosa layer composed of non keratinized stratified squamous ET which can take damage.
Also composed of simple columnar ET w/ goblet cells
Lamina Propia
In mucosa layer composed of areolar CT w/ blood vessels, lymphatic vessels, nerves, and MALT
Muscularis mucosae
In mucosa layer composed of smooth muscle that can dislodge stuck particles
Submucosa
Made of areolar CT w/ blood vessels, lymphatic vessels, nerves, and MALT. Also contain submucosal nerve plexus
Musularis externa
Made of inner layer of circular and outer layer of longitudinal arranged smooth muscle. Also contain myenteric nerve plexus
Serosa
Is seen if organ is within abdominal cavity
Adventitia
Is seen in outer layer if organ is outside of abdominal cavity
Intrinsic Innervation
Comes from enteric nervous system.
Includes: submucosa plexus and myenteric plexus
Submucosa nerve plexus
(Occurs via intrinsic innervation)
Located in submucosa that regulates digestive secretion and reacts to the presence of food
Myenteric nerve Plexus
(Occurs via intrinsic innervation)
Located in muscularis mucosae that controls motility
Extrinsic Innervation
By autonomic nervous system.
Includes: SNS & PSNS
Sympathetic Nervous System
(Occurs via extrinsic innervation)
Inhibits the digestive process, “fight or flight”
Parasympathetic Nervous System
Digesting occurs, “rest & digest”
Short Reflexes
Involves the intrinsic nerve plexuses that occurs entirely within the gastrointestinal wall. Wall can sense change via receptors and respond accordingly with effectors such as smooth muscle or glands
Long Reflexes
Extrinsic innervation that involves CNS and ANS.
Enteroendocrine cells
Secretes GI hormones into the blood stream to travel to the target organ
Peritoneum
In abdominal cavity that contain serous membranes
Parietal peritoneum
Lines wall of abdominal cavity
Visceral peritoneum
Lines outer layer wall of organ
Peritoneal cavity
Between visceral and parietal peritoneum. Filled with peritoneal fluid to reduce friction of moving organs
Peritoneal fold
Mesenteries: double serous membrane that provides a pathway to get vessels and blood from posterior wall out to organs suspended within the abdominal cavity
Retroperitoneal organs
Located outside the peritoneum and most often in back body wall. Examples: kidney, spleen, and duodenum
Function of Peritoneal fold
Provide nutrients, oxygen, lymphatics, and nerves to organs that are suspended within the abdominal cavity
Mesocolon
A mesentery that attaches the transverse colon to the mesocolon
Greater omentum
Attaches the greater curvature to the transverse colon
Lesser omentum
Attaches the lesser curvature to the liver
Falciform Ligament
Attaches the right and left lobe of liver
Functions of oral cavity
Ingests food, mastication to create bolus, begins chemical digestion of carbs, and moves food to pharynx
Salivary amylase
A carb digesting enzyme secreted by salivary glands to start digestion
What is oral cavity lined in?
Lined in non keratinized stratified squamous ET for protection against heat, chemicals, and abrasion
Tongue
An accessory digestive organ that sits in oral cavity lined in non keratinized stratified squamous ET
Filiform Papillae
“spiky like structures” that gives surface grip. No taste buds.
Fungiform Papillae
Contains taste buds, located towards front of tongue
Vallate Papillae
10-12 of them in an inverted V located in back of tongue. Contain very deep crips with taste buds
Teeth location?
In mandible and maxilla
Dentin
Bone-like tissue that is avascular
Pulp cavity
Contain blood vessels and nerves that supply the teeth
Enamel
Covers crown of teeth. Hardest substance in body that contains hydroxyapatites
Function of teeth?
Mastication
Location of minor salivary glands?
Mouth and tongue
Loaction of major salivary galnds?
Outside oral cavity
Function of major salivary glands
Secrete saliva. EX: parotid glands, submandibular glands, and sublingual glands
Saliva composition
Mostly water (98-99.5%). Contain ions (bicarbonate, K+, Cl), salivary amylase, proteins (mucin, lysozyme, lgA), and nitrogen containing metabolic wastes
Digestion of carbs begins where?
In oral cavity because salivary amylase digest carbohydrates
Submandibular glands contain what cells?
Both serous and mucous cells
Parotid glands contain what cells?
Mostly serous cells
Sublingual glands contain what cells?
Mostly mucous cells
Function of minor salivary glands?
Keep mouth moist by secreting low volume of saliva
Taste receptors pick up?
Taste chemicals; leads to increase in saliva production
chemoreceptors pick up?
Chemicals in food we eat; leads to increase in saliva production
Mechanoreceptors pick up?
Can sense presence of food in the mouth; leads to increase in saliva production
Irritated G.I tract stimulates will cause?
Will increase salivation
Location of salivatory nuclei
Brainstem in pons
Parasympathetic impulses do what to oral cavity?
Produce more saliva in major glands
Sympathetic impulses do what to oral cavity?
Inhibit salivation resulting in dry mouth
Pharynx passage
mouth to oropharynx to laryngopharynx
Pharynx routes food and fluid to?
The epiglottis
Pharynx routes air to?
Larynx then trachea
What ET lines pharynx?
Non-keratinized stratified ET due to abrasion
Deglutition
Process of swallowing
Voluntary phase
Having concious control of swallowing via pushing tongue against roof of mouth and pushing bolus back
Pharyngeal phase
Involuntary controlled by medulla
Esophageal phase
Involuntary controlled by medulla.
Layers in esophagus?
Contains all 4 alimentary canal layers. Mucosa, submucosa, muscularis externa, and adventitia.
How many phases of deglutition?
3
Stomach functions
Mechanical digestion, chemical digestion, and can absorb very little
Pepsin
A protein digesting enzyme in stomach
Gastric lipase
A fat digesting enzyme in stomach
How does chyme form?
Stomach juices mix together with bolus to form pasty acidic chyme
Chyme is delivered to
C shaped duodenum
Function of rugae
Folded wrinkle bits covering entire stomach that can stretch or decrease in shape when empty
Mucosa layer in stomach contains
Gastric pits and gastric gland
Gastric pits are lined in?
Mucus cells that serve for mucous secretion
Gastric glands contain?
Gastric juice that is very acidic