Gastrointestinal System Flashcards
What are the 3 main components of the digestive system?
- digestive tracts
- accessory organs
- cell lining and tissue components
What are the functions of the GIT?
- ingestion
- mechanical digestion and processing
- chemical digestions
- secretion (e.g. enzymes, acids, salts) by glandular organs
- absorption of vitamins, nutrients, water and minerals
- defecation (waste elimination through the anus)
- defence
What are the 7 components of the oral cavity?
- lips
- front 2/3 of tongue
- floor of the mouth
- buccal mucosa
- upper and lower gingiva
- retromolar trigone
- hard palate
What is the hard and soft palate respectively?
- hard = front part of roof of mouth
- soft = back part
What are functions of the oral cavity?
- mastication and lubrication to produce a bolus
- gustation (taste)
- limited chemical digestion of glucose and lipdis
What are functions of the uvula?
- secrete saliva to moisten the mouth and throat
- prevents food and liquid from going up the nose (along with soft palate)
What are functions of the tongue?
- mechanical digestion
- manipulation of food
- sensory taste and temperature
- lubrication via mucin, water and lingual lipase
What are teeth required for?
tearing and grasping food (mastication)
What do the major salivary glands do?
work together to keep the mouth moist and help with digestion
What are the 3 major salivary glands?
- parotid glands
- submandibular glands
- sublingual glands
Where are the parotid glands and what do they produce?
near the back of the jaw just in front of the ears and produce serous secretion to help with chewing and swallowing
Where are the submandibular glands and what do they produce?
under the jaw and produce a mix of mucus and saliva
Where are the sublingual glands and what do they produce?
under the tongue and produce saliva that is mostly mucus
What do minor salivary glands secrete?
mucous
What is the difference between serous and mucous cells?
- serous cells have spherical and vesicular nuclei and secrete a more watery substance
- mucous cells cytoplasm and nuclei are pushed against the basal cell membrane and secrete mucin
What are functions of saliva?
- lubricate and moisten the bolus
- dissolve chemicals for gustation
- act as a buffer
- control oral bacteria population via antibodies and lysozymes
- salivary reflex
What is the pharynx (throat)?
the muscle-lined space that connects the nose and mouth to the larynx and oesophagus
What is the larynx?
the upper opening into the trachea (windpipe)
What are the 4 phases of swallowing?
- buccal phase - voluntary phase where the tongue pushes the bolus to the back of the mouth towards the pharynx
- pharyngeal phase - involuntary phase begins when the bolus reaches the back of the throat which triggers a reflex that closes off the airway and moves the bolus down through the pharynx to the oesophagus
- oesophageal phase – involuntary phase where the bolus is pushed down the oesophagus towards the stomach by peristalsis
- bolus enters the stomach by triggering the opening of the lower oesophageal sphincter
What is mucosa?
the moist, inner linings of organs and body cavities
What are the 3 layers of mucosa?
- mucosal epithelium
- lamina propria
- muscularis mucosae (deepest and most active)
What parts of the digestive system have stratified squamous epithelium?
- oral cavity
- pharynx
- oesophagus
- anal canal
What parts of the digestive system have simple columnar epithelium?
- stomach
- small intestine
- large intestine
What is the muscularis mucosae made up of?
smooth muscle and elastic fibres that regulate contraction of the lumen
What are the 2 layers of the muscularis mucosae?
- inner – circular muscle
- outer – longitudinal
What is the submucosa?
a connective tissue layer that binds the mucosa and muscular layer
What does the submucosa contain?
- blood vessels, lymphatic vessels and nerve fibres
- exocrine glands that secrete buffers and enzymes in the lumen of digestive tracts
Why is the mucosa lined close to the muscular layer?
for protective functions, effective nutrient absorption and coordination of functions
What is the muscular layer movement of the mucosa coordinated by?
the enteric nervous system which innervates the myenteric plexus
What do pacesetter cells do?
spontaneously trigger action potentials and contractions in the muscle
What is peristalsis?
the rhythmic wave of contraction that propels the bolus
What is segmentation?
the back and forth movement caused by a local reflex in the small and large intestines required to churn, fragment and mix the stomach contents in no pattern or specific direction
What does the oesophageal submucosa contain?
- oesophageal glands that secrete mucous
- a muscular layer containing superior skeletal and inferior smooth muscle
What does the adventitia do?
anchor the oesophagus to the posterior body wall
What do the upper and lower oesophageal sphincters do respectively?
- upper prevents air flowing into the oesophagus while breathing
- lower prevents food from flowing back up the oesophagus
What is the peritoneum?
the serous membrane that lines the abdominal cavity composed of mesothelial cells supported by a thin layer of fibrous tissue
What are mesenteries?
double sheets of peritoneal membrane that stabilise digestive tracts and prevent volvulus
What does the lesser omentum hold?
the liver and top part of the stomach
What does the greater omentum hold?
the bottom part of the stomach (pouch of adipose tissue)
What is the falciform ligament?
a thin, sickle-shaped, fibrous structure that connects the anterior part of the liver to the ventral wall of the abdomen
What is the mesentery proper?
the mesentery for the duodenum (small intestine) and pancreas