4.Digestive system Flashcards
define digestion
the breakdown of large insoluble molecules into small soluble molecules by chemical and physical (mechanical) means
Features of mechanical digestion
-breakdown of food by (chewing, swallowing and muscular movements) into smaller pieces, increasing their SA without changing their chemical composition
Features of chemical digestion
-chemical decomposition of food via enzymes and acids (mouth, stomach and intestine)
eg of mechanical digestion
-chewing food/mastication -teeth
-muscular bags (smooth muscle in stomach) churns food
eg of chemical digestion
-HCL in stomach and salivary amylase in mouth (saliva)
overview of digestion
1.ingestion via mouth
2.mechanical an chemical breakdown of food
3.nutrient absorption in small intestine
4.elimination of waste via anus
identify pathway of food through gastrointestinal tract
mouth (teeth), pharynx, oesophagus, stomach, small intestine, large intestine, rectum, anus,
3 parts of small intestine
duodenum
jejunum
ileum
parts of large intestine
caecum
ascending colon
transverse colon
descending colon
sigmoid colon and rectum
three salivary glands
sublingual gland (below tongue)
submandibular gland (below mandible)
Parotid gland (below ears)
function of mouth
to mechanically (teeth) and chemically (saliva) breakdown food
function of oesophagus
transport food bolus from mouth to stomach via peristalsis
function of stomach
-to mechanically (churn food through muscle contractions) and chemically breakdown food (through HCl)
-create pepsin (break down protein)
-secrete mucus that lubricates the stomach walls
small intestine function
absorb nutrients into bloodstream
large intestine function
-absorb water and electrolytes converting liquid chyme into semi solid (stool)
-form and propel faeces
-chemically digest food molecules using gut microbes
rectum function
store (temporarily) faeces
anus function
transport / provide pathway for faeces out of body-defecate
salivary glands function
lubricate food- making it easier to pass through digestive system
chemically digest food (salivary amylase)
destroy ingested pathogens (non specific)
pancreas function
regulate BGL via hormones (use insulin via endocrine gland)
produced and release enzymes for digestion (in pancreatic juice)
liver function
secrete bile
metabolise fats, carbs and proteins
removes toxins
gall bladder function
store, concentrate and release bile
sphincter function
smooth muscle (circular) that closes off the stomach after a meal
Identify the processes of digestion
Ingestion, propulsion, digestion, absorption, assimilation and elimination
Define ingestion
intake of substances, passing of food or liquid from mouth into alimentary tract
Define propulsion
movement of foo/liquid along GI tract
Structure of stomach
Muscular bag on the left side of the abdominal region and posterior to liver
-C shaped (4 regions)
Identify 4 regions of stomach
cardia
Fundus
Body
pylorus
Define absorption
move digested food molecules across intestine wall into blood or lymph
Structure of small intestine
-25 cm wide and 5 m long
-joins and becomes large intestine
Features of the small intestine to aid function
-single wall of columnar epithelial cells, short diffusion pathway, increased rate of diffusion
-finger like projections (villi and microvilli), increaseSA of small intestine for absorption, increase rate of diffusion
-each villus has large capillary network and lacteal, increase SA, increase rate of diffusion
-mucous membrane, moist, protect intestine and provide lubrication (dissolve in solution)
Structure of duodenum
1st part of small intestine, 25 to 30 cm long
Function of duodenum
-final stage of digestion occurs here
-secretin produced here to respond top acidic chyme (maintains pH)
Structure of jejunum
2 m long, lined by villi and microvilli, middle section of small intestine
Function of jejunum
absorb nutrients (90% of absorption)
Structure of ileum
end section, 3 m long
Function of ileum
absorb nutrients into blood
define assimilation
movement of digested food molecules from bloodstream into cells
Structure of pancreas
located in abdominal region, posterior to stomach, connected to duodenum by pancreatic duct
Pepsin
made in stomach and breaks down proteins
Secretin
made in duodenum and responds to acidic chyme
amylase
made in pancreas and salivary glands and breaks down fats/lipids
lipase
made in pancreas and breaks down fats/lipids
trypsin
made in pancreas and breaks down proteins
What is bile
water, mucous, mineral salts, bile pigments, bilirubin, bile slats and cholesterol
function of bile
digest insoluble fats
metabolise and absorb vitamins (KDEA)
excrete bilirubin
Define excretion
excretion of undigested food substance through anus after processing in blood
Structure of large intestine
1.5 cm long, in-between small intestine and anus
How are faeces formed
- Undigested food (chyme) enters colon from intestine
- H2O, salts and vitamins are reabsorbed
- Dehydration and compaction of undigested matter
- Semi solid faeces forms / stool
What is faeces made of
60-70% water, fibre, dead and alive microbes, epithelial cells, fatty acid, mucous
Rectum structure
starts at sigmoid colon and ends at anal canal, 13 cm long
Structure of anus
-At end of digestive system (external opening)
-contains inner and external sphincter
Inner sphincter
is smooth muscle and involuntary
External sphincter
is skeletal muscle and voluntary
