Week 10a GI Tract Flashcards
What are the General functions of the digestive tract?
- Motility – movement (of bolus through our gastrointestinal tract)
- Secretion - substances are produced and discharged to assist with digestion
- Digestion - breakdown of food molecules to be absorbed
- Elimination - the removal of waste products (AKA defacation)
The parts of the intestinal tract in order (superior to inferior)
- Mouth
- Pharynx
- Oesophagus
- Stomach
- Small intestine
- Large intestine
What kind of membrane is the oesophagus and intestines lined with?
Epithelial membrane
Digestive functions
- Ingestion - Taking food/liquids into mouth
- Secretion - Addition of water, acids, buffers and enzymes into GI tract
- Mechanical processing (Motility):
- Physical breakdown of food into smaller particles
- Mix with secretions
- Move contents towards anus
Processes of GI tract
- Digestion - Chemical digestive enzymes chemically breakdown large molecules into smaller molecules
- Absorption - Uptake of nutrients through epithelial cells into blood or lymph
- Defecation - Elimination of wastes, indigestible substances, bacteria, dead cells etc.
What are the mechanical processes of digestion and where do they occur
- Mouth - Chewing and swallowing
- Oesophagus – Peristalsis
- Stomach - Mixing, churning (through muscle contraction, enzymes and acids to create chyme)
- Small intestine:
- Segmentation
- Peristalsis
What is Peristalsis?
Squeezing of muscles in a wave like pattern to move the bolus down the oesophagus to get to the stomach. Also occurs in the small intestine.
What is the function of the mouth?
- Mastication occurs in the mouth – food needs to broken down into an appropriate sized bolus to allow for swallowing. This is achieved by the following structures:
- Teeth for chewing and grinding, Increases surface area of food particles
- Tongue manipulates food between teeth
- Palate separates oral cavity from nasal cavity, is a rough surface and helps tongue manipulate food
Name the main parts of the pharynx
Nasopharynx
Oropharynx
Laryngopharynx
What are the functions of the pharynx?
- Respiratory function (Nasopharynx)
- Respiratory and digestive function (Oropharynx Laryngopharynx)
- Swallowing:
- Initially voluntary (skeletal muscles)
- Then involuntary (smooth muscle)
- Muscles contract to move bolus into esophagus
What is the Oesophagus (~esophagus)
- Collapsible muscular tube - The upper third consists of striated muscle, and the lower two-thirds consists of smooth muscle.
- Posterior to trachea
- Moves bolus from pharynx to stomach via peristalsis
- Two sphincters (Keeps esophagus closed to avoid acid moving superiorly and causing heartburn sensation)
- Upper esophageal sphincter - regulates movement into esophagus
- Lower esophageal sphincter - regulates movement into stomach
- It is innervated by the vagus and sympathetic divisions of the nervous system
- The vagal activity increases esophageal activity
A major function of the upper digestive system is?
a. absorption of H2O
b. absorption of protein
c. begins digestion of lipids
d. transports food & fluids from mouth to stomach
d. transports food & fluids from mouth to stomach
Functions of the stomach
- Storage of ingested food
- Very distensible
- Muscular wall allows mechanical digestion (creates chyme)
- Pyloric Sphincter stops chyme moving past stomach too early
What are the parts and functions of the small intestine?
- Duodenum
- Receives chyme and digestive secretions
- Neutralises stomach acids
- Jejunum
- Chemical digestion
- Nutrient absorption
- The Ileum
- Ends at ileocecal valve (sphincter)
Mechanical functions of small intestine
- Mixes chyme with secretions
- Increases absorption
- Moves residue forward
- Begins with segmentation
- Does not follow a set pattern
- Enhances digestion and absorption
- Followed by peristalsis
- Moved residue towards large intestine
