Digestive System Flashcards
What is the Digestive System also referred to as?
Digestive tract
Gastrointestinal tract (GI Tract)
Alimentary canal
What is the anatomy of the DS?
Oral cavity Pharynx Oesophagus Stomach Small intestine Large Intestine
What are the accessory organs and glands of the digestive system?
Teeth Tongue Salivary glands Liver Gall bladder Pancreas
What is the energy requirement of the human body at rest and how is it obtained?
30kcal/kg of body weight per day.
Ingestion of food, usually a blend of different types of complex nutrient macromolecules such as carbohydrates, proteins, lipids.
Subunits of complex molecules can be used by our cells for:
Energy generation (ATP)
Cell growth
Cell repair
Where is ATP produced in our cells?
mitochondria
Digestive system provides essential nutrient subunits from complex foods through the integration of what processes?
ingestion propulsion mechanical digestion chemical digestion secretion absorption
eliminates indigestible waste material by:
excretion/defecation
What is ingestion?
The process of introducing food and liquid nutrients into the digestive tract via the oral cavity (OC)
What is propulsion?
The process that moves food through the DS at a rate that permits optimal digestion and absorption.
Includes: Deglutition and Peristalsis
What is Deglutition?
Swallowing food
What is Peristalsis?
Successive waves of contraction and relaxation of smooth muscle layers in gut wall.
What physiological stimuli initiate peristalsis?
Mucosal pinching
Mechanical distention with gas, liquid or solid bolus.
Describe mechanical digestion in the oral cavity:
Solid foods mechanically processed by chewing (mastication) and shearing action of teeth.
Food mixed with saliva by tongue to form food boluses.
Reducing size of ingested food to increase surface are so chemical digestion is more efficient.
Describe chemical digestion in the oral cavity:
Saliva contains enzymes to breakdown complex macromolecules.
Amylases for carbohydrates
Lipases for lipids
Describe mechanical digestion in the stomach:
Muscles in the stomach allow Churning of food
Describe the chemical digestion in the stomach:
Hydrochloric acid and pepsin in the stomach allow for the digestion of proteins.
Describe mechanical digestion in the small intestine:
Segmentation movements of gut wall ensure food is mixed well with digestive enzymes
What is secreted during the digestion of food to act as an aiding accessory?
Saliva - Amylase and Lipases Gastric juice - HCl and Pepsin Bile Alkaline mucous Pancreatic Juice
How is the small intestine adapted for nutrient absorption?
Villi (projecting structures) allow for larger surface area for more absorption.
Villi are one cell thick - small diffusion distance
Lots of them
The gut wall consists of 4 major layers, what are these?
- Mucosa
- Submucosa
- Muscularis externa
- Serosa/adventitia
The mucosa (mucous membrane) consists of what structurally?
- Epithelium - may be simple or stratified
- Lamina propria - highly vascular loose connective (areola) tissue, rich in lymph vessels, lymphoid cells (mast cells), smooth muscle cells, sensory nerve endings, mucous secreting cells)
- Muscularis mucosae
What is the function of the mucous membrane?
Protective against pathogens and dirt.
Where in the small intestines would you expect mucosa to be most developed?
Duodenum
What are the three parts of the small intestines?
Duodenum - Most digestion
Dedunum - Most absorption
Ileum - important absorption
What is the structure of Submucosa?
Thick irregular layer of connective tissue
Rich in blood vessels
Contains lymph vessels, glands, lymphoid tissue(MALT)
Contains submucosal plexus
What is the submucosal plexus and what is its function?
Nerve fibres braided together to form plexus.
Innervates blood vessels to change diameter
Glands to secrete enzymes
Muscularis mucosa to change diameter
What is the structure of the muscularis externa (ME)?
Made up of two muscle layers:
Circular muscle
Longitudinal muscle
What is the function of the circular muscle in the muscularis externa?
Narrows lumen through contraction to mix and segment food and form sphincters
What is the function of the longitudinal muscle in the muscularis externa?
Shortens tube during contractions to help move food along the digestive tract during peristalsis
What is the enteric nervous system (ENS) made up of?
Most external layer
Double membrane layer of epithelial cells
Visceral - stuck to organ
Parietal - closer to cavity
Serosa and adventitia
What are serosal membranes and what are their function within the ENS?
Surrounding organs that sit within the peritoneal cavity
e.g stomach, spleen, liver
What are adventitia and their function within the ENS?
Loose connective tissues to hold organs into place.
Outside peritoneal cavity
e.g pancreas, duodenum, ascending and descending colon
What is the myenteric plexus?
Plexus of neurons in the longitudinal and circular muscle layers of the muscularis that control the contraction and relaxation of the smooth muscles in the ME.
What is the oral cavity comprised of?
(or buccal cavity) The lips - Anterior boundary The cheeks - Lateral boundary Palate - Superior boundary Tongue forms inferior boundary
What is the cavity lined by?
Stratified squamous epithelium
The gingiva (gums) are covered by what?
protective layer of keratinised epithelial cells
What are the different parts of the Palate?
Anterior - Hard Palate
Posterior - Soft Palate
What is a common congenital disorder that results in malformation of the hard palate?
Cleft palate
When does fusion of the palatine shelves to form the palate occur?
During the 7th week of embryonic development