Digestive system Flashcards
What is A and what is its function?
Mouth
To mechanically (teeth) and chemically (saliva) to breakdown food
What is B and what are its 4 functions?
Tongue
- moves food bolus towards teeth during mastication so it can be mechanically digested
- moves food bolus towards back of throat so it can be swallowed
- speech
- taste
What is C and what is its function?
Oesophagus
To transports food bolus from the pharynx to the stomach via peristalsis
What is D and what is its function?
Liver
To produce bile that metabolizes fats, carbohydrates and proteins
What is E and what is its function?
Gallbladder
To store, concentrate and release bile
What is F and what is its function?
Duodenum
finial stage of digestion
secretin produced in response to acidic chyme in order to maintain pH (homeostasis)
What is G and what is its function?
Jejunum
lined with villi and microvilli
to absorb nutrients e.g. proteins, CHO, vitamins etc
What is H and what is its function?
Ileum
lined with villi and microvilli
to absorb nutrients and most water
What is I and what is its function?
Anus
To transport/provide pathway faeces out of the body
What is J?
Parotid gland (below ears)
What is K?
Sublingual gland
What is L?
Submandibular gland
What is M ?
Pharynx
What is N and what is its function?
Stomach
a C-shaped muscular bag located in the LUQ
To mechanically (churning of food through muscle contractions) and chemically breakdown (through activating enzymes eh. HCL)
What is P and what is its function?
Pancreas
To regulate of blood sugar levels (hormones)
To produce and release enzymes for digestion
What is Q?
Transverse colon
What is R?
Ascending colon
What is S?
Descending colon
What is W and what is its function?
Rectum
contains stretch receptors which send a message to nervous system to stimulate voluntary contraction of anal sphincter to push out faeces
To store faeces
What is the function of the digestive system?
To break chemically and mechanically down ingested food, absorb nutrients and excrete waste products.
what is a bolus
semi-solid mass of food
function of the small intestine
duodenum, jejunum, ileum
to absorb nutrients into the bloodstream e.g. carbohydrates/lipids/proteins
Function of the salivary glands
To lubricate food to make it easier to move through digestive system
To chemically digest foods via enzymes
To destroy ingested pathogens (Non-specific immune defence)
function of the uvula
helps guide food bolus down the oesophagus and prevent food going up the nose
describe how the food bolus moves from the oral cavity to the oesophagus
tongue pushes food to back of oral cavity
epiglottis ensures food bolus moves down pharynx and not trachea
bolus goes down oesophagus
describe 4 features of the small intestine that assist with its function
- thin walls= short diffusion pathway= increased rate of nutrient diffusion
- rich blood supply to villi= maintain conc grad
- contains villi (finger-like projection) = large SA:V ratio= increased rate of absorption
- mucous membrane secretes mucus= moist= provides lubrication to reduce friction from movement of chyme
what is chyme?
mixture of food, gastric juice and HCl created in the stomach
What is C?
Jejunum
What is D?
Ileum
What is E?
Large intestine
Where is pepsin produced and what does it breakdown?
Produced = Stomach
Breaksdown = Proteins
Where is secretin produced and what does it breakdown?
Produced = Duodenum
Function = regulate gastric acid
Where is amylase produced and what does it do?
Produced = pancreas and salivary glands breaksdown = starch
Where is lipase produced and what does it do?
Produced = pancreas
breaksdown = fats/lipids
Where is trypsin produced and what does it do?
produced =pancreas
breaksdowns = proteins
insulin
increase uptake of glucose into cells with excess being converted to glycogen –> decreasing BGL
Glucagon
breaks down stored glycogen into glucose which enters the blood stream –> increasing BGL
GI
gastrointestinal
Epiglottis
To provent food from going into the trachea and the rest of the respiratory tract
Allows air to pass into the trachea
Segmentation occurs in the
Small intestine
6 Digestive Activities
- Ingestion
- Propulsion
- Mechanical Digestion
- Chemical Digestion
- Absorption
- Defecation
Digestive Activities
Ingestion
Taking in food by the mouth
Digestive Activities
Propulsion
Aids in moving the food along the gastrointestinal tract
- swallowing (voluntary)
- peristalsis (Involuntary)
Peristalsis
involuntary alternating waves of contractions and relaxation
Digestive Activities
Mechanical Digestion
- physically prepares the food for chemical digestion by increasing surface area
- eg. mastication, churning of food in stomach, segmentation along the small intestine
Digestive Activities
Chemical Digestion
- Complex food molecules are broken down to chemical building blocks by enzymes
- Begins in the mouth and is completed in the intestines
Digestive Activities
Absorption
- Passage of digestive end products along with vitamin, minerals and water from the lumen of the gastrointestinal tract to the blood or lymph
- Major site of absorption is the small intestine
Digestive Activities
Defecation
indigestible substances are eliminated from the body in the form of faeces
3 Regulatory Mechanisms of the Digestive System
- Mechanical/Chemical Stimuli
- Reflect activity - Hormones
- Within the stomach and small intestine - Neurons. Two Types:
- Intrinsic (short reflexes) –> within the GI tract
- Extrinsic (long reflexes) –> inside or outside the GI tract.
Deglutination (Process of Digestion)
- Ingestion
- The intake of food, which includes mechanical digestion and chemical digestion (salivary amylase and lingual lipase). Voluntary and reflexive. - Buccal Phase
- Propulsion of the bolus into the oropharynx and then into the laryngopharynx (passageways for food, fluids and air). Multi-layer epithelial cells - protect pharynx. Skeletal muscles to contract and propel food. - Pharyngeal Phase
- food moves from the laryngopharynx and is directed to the oesophagus. Epiglottis closes off the larynx to incoming food. Respiration is inhibited. Bolus moving from pharynx to oesophagus by peristalsis is involuntary. - Esophageal Phase
- The lower oesophageal sphincter opens to allow the bolus to pass into the stomach. Bolus from oesophagus to stomach by peristalsis is involuntary.
Regulation of Gastric Secretions (Juices)
- Cephalic Phase:
- Hypothalamus received stimulus from tastebuds, stimulates medulla
- transmits impulses which result in secretory and contractile activity.
- Initiated by the taste, sight, smell or thought of food.
- Inhibited by loss of appetite or depression. - Gastric Phase:
- Occurs once food enters the stomach.
-Neural and hormonal stimuli
- Initiated by food entering the stomach.
- Inhibited by excessive acidity in the stomach, and emotional upset. - Intestinal Phase:
- Initiated by food entering the duodenum.
- Inhibited by enterogastric reflex, and intestinal hormones.
4 Structural Modifications of the Small Intestine
Circular Folds
- Increases surface area and causes chyme to spiral around the small intestine
Villi
- Finger-like projections of the mucosa that increase surface area Microvilli
- Contain Enzymes for absorption
Cilli
- Movement of food across the tract
Absorptive State
when you have just eaten
Post-Absorptive State
when you have not eaten
Sources of Blood Glucose
Carbohydrates
Triglycerides
Amino Acids
Gluconeogenesis
Converts amino acids into keto acids into glucose. (postabsorptive)
Glycogenolysis
Converts glycogen into glucose. (postabsorptive)
Glycogenesis
Converts glucose into glycogen. (absorptive)
Lipolysis
Converts triglycerides into fatty acids. (postabsorptive)
Lipogenesis
Converts fatty acids into triglycerides. (absorptive)
structure of digestive system
- THE ALIMENTARY CANAL
- Continuous Muscular digestive tube: digests the food into smaller fragments and absorbs fragments into the blood. - ACCESORY DIGESTIVE ORGANS
- Organs that aid the digestive process.
4 layers of small intestine
mucosa, submucosa, muscularis externa, serosa
What sphincter separates the stomach from the duodenum?
Pyloric sphincter
function of large intestine
to absorb water and ions
REGULATORY MOVEMENTS of large intestine
- HAUSTRAL CONTRACTIONS: SLOW SEGMENTING MOVEMENTS (30 MINS)
- MASS MUSCLE MOVEMENTS - LONG SLOW MOVING CONTRACTIONS USUALLY DURING/AFTER EATING
- RECTAL WALL INITIATES DEFICATION REFLEX.
- DEFICATION IS ASSISTED BY VALSALVA’S MANEUVER
- Closing of glottis, contraction of diaphragm and abdominal wall muscles to increase intra- abdominal pressure.
–> 1 - faeces move into, exited rectum - stimulate stretch receptors
–> Parasympathetic signals - signal contraction, relaxation of anal sphincter
–> Voluntary motor neuron inhibits allowing anal sphincter to relax.
SUBMANDIBULAR GLANDS
- 70%
- Mixture of water and mucous
SUBLINGUAL GLANDS
- 5%
- Mucous
PAROTID
- 20%
- WATERY
