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
A major function of the small intestine is to:
a. absorb the digestive enzymes
b. produce acid to help breakdown foods
c. absorb nutrients from broken down foods
d. neutralise digestive enzymes
c. absorb nutrients from broken down foods
What are the parts of the large intestine?
- Cecum
- Colon
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
- Rectum
- Anal canal
- Internal anal sphincter
- External anal sphincter
- Anal canal
Functions of large intestine
- Absorption of vitamins produced by bacteria
- Reabsorption of remaining water
- Compaction and storage of feces prior to defecation
- Produces mucous for lubrication
- Motility
- Haustral contractions every 30 mins
- Mass movements 1-3 times/day, lasting 15 mins
