Digestive system Flashcards
What is the function of mesenteries?
Mesenteries help suspend and stabilize organs during digestive movement by anchoring abdominal organs to the peritoneum.
What is the peritoneum?
The peritooneum is a double-llayered serous membrane encasing most of the abdominal cavity.
Which systems coordinate digestion?
- The autonmic nervous system -
- Entric nervous system (organized into two systems)
2a. Submucosal plexus
— Contain sensory fibres, paraasympathetic and synmpathetic postgangionic neurons
— For determining nutrient levels
2b. Myenteric plexus
— contains ENS neurons (interoneurons and motor neurons)
— For coordination of system
What smooth muscle layers are found in most of the digestive tract?
- Circular layer
— Arranged around the circumference of the tube (inner) - Longitudal layer
— Arranged along the length of the tube (outer)
What are the key exceptions to the two layer smooth muscle organization of the digestive tract? How do they differ?
- Oral cavity, pharynx, upper esophagus
— Have skeletal muscle in muscularis - Stomach
— Has three layers
—— Oblique, circular, longitudinal - Colon
— Has an incomplete longitudinal layer
What are pacesetter cells and where can the be found?
Pacesetter cells create regular intrinsic rhythms of depolarization and repolarization which spread throughout the muscle layer of visceral smooth muscle cells.
— These rhymic depolarization is not enough to trigger an action potential but only sensitizes the tract.
In the digestive system, which division of ANS enhances muscle activity and which receptor does it interact with?
Parasympathetic division enhances the digestive system and excites muscarinic receptors through the release of acetylcholine
Define the difference between the terms: ingestion, digestion, and absorption.
Ingestion: the act of taking food (or water) into the body. Interaction of external substance to internal system
Digestion: the process of extracting and breaking down substance into key nutrients
Absorption: the process of moving nutrients from inside the digestive system into the interal system for nutrient utilization.
What is propulsion and how is it done in the digestive system?
Propulsion is the movement of ingested material through the digestive tract
This is done through peristalsis - waves of contraction through signaling of stretch receptors in the digestive system.
— Circular muscles contracting behind the bolus while longitudinal miuscels contracting head of bolus
What is are the two types of digestion? How is segmentation involved?
Physical digestion: fragmentation of food by purely physical forces
Chemical digestion: breakdown of macromolecules into smaller components by chemicals or enzymes
Segmentation is involved in the rhymic cylces of circular muscle contration to help continue fragmenting the bolus
— dos not produce net foward movement
What do secretions do in the digestive system and how efficient is reabsorbition?
Secreted fluid contains digestive enzymes or chemicals and help reduce friction of food moving through the tract
Almost all of these secretions are reabsorbed before waste (~150 mL lost in feces from 2200 mL food and drink intake)
What are the five processes and which of them do not occur in the oral cavity?
Five processes: Digestion, propulsion, absroption, coordination, protection
Absorption
Reasoning
Digestion: chemical (salivary enzymes) and physical (mastication) digestion occurs
Propulsion: Tongue
Coordination: Taste buds contain receptors that coordinate digestive and physical movement to ensure proper digestion of the food. (Saliva secretion increase from food ingestion)
Protection: Saliva secretion prevent substances from damaging esophoagus
What is mastication?
The physical digestion of food by bringing two rows of teeth together.
This is a coordinated rhymic motor behaviour involving movements of manible
How does the tongue contribute to the digestion process
Tongue is a musclar organ containing skeletal muscle tissue.
Contributes to
— physical digestion and propulsion
— secretes lingual lipase for chemical digestion of fats
— principal organ for sense of taste (gustation)
What digestive reflexes do taste cells signal?
- remember Tongue > papillae > taste buds
Long refelzes triggered
— salivation reflex
— Gag reflex
— Gastric reflexes
What is found in saliva?
Saliva is an aquesous solution (>99% water) but also contains a digestive enzyme (salivary amylase), antibactreial enzymes and anitbodies, and electrolyes that buffer the osmolarity and pH of the orla cavity.
How is the ANS division involved in the salivortory reflex?
Salivatory reflex is a long reflex that activates from chemoreceptors in taste cells and mechano receptors i nthe oral cavity. These signals are integrated into the brain through the medulla.
Parasymapthetic activity enhances the rate of salivary secretion
sympathetic acitivy stimualtes secretion by reducing the bolume of saliva produced
What are the three phases of swallowing?
- Buccal phase (voluntary)
— Tongue elvates and pushe bolus against the hard palate
— Tongue retracts, forcing bolus into oropharynx - Pharyngeal phase (refelxive)
— Peristaltic-like contraction of pharngeal muscle triggered when bolus in oropharynx
— Larngeal and hyoid muscles contract to elevate larynx and close trachea with epiglottis
— Muscles in soft palate elevate uvula to block nasopharnyx - Esophageal pahse (reflexive)
— Persitalitic contractions begin when bolus enter esophagus (neural activity in the myenteric plexus coordinate wave-like action)
— Distal end of esophagus contain stretch receptors that trigger relaxation of smooth muscle in the lower esophageal sphincter
WHOLE PROCESS TAKES ABOUT ~9s
What processes are found in the esophagus?
Five processes: Digestion, propulsion, absroption, coordination, protection
Found in the esophagus
— Propulsion: movement of food down the esophagus through peristalsis
— Coordination: Preps stomach for food
— Protection: Mucosa layer precent pathogen and acid reflux from damaging the walls of the esophagus
— Digestion?
Predict what would happen to the set of movements that occur during swallowing if your rate of saliva secretion was reduced. Would they increase or decrease?
There would be decreased movement during swallowing if saliva secretion is lowered because there would be more friction which would make propulsion of bolus harder.
