Digestion Flashcards
Extracellular Digestion
Digestion occurs within cavities.
Ingestion, digestion, absorption assimilation and egestion
Alimentary cand extends
from… to …
Mouth to anus
Alimentary canal consists of
Oral cavity
Esophagus
Stomach
Small intestine (duodenum,jejunum,ileum)
Large intestine (caecum, colon)
Saliva secreted by 3 pairs of salivary glands known as
- Sublingual glands
- Sub maxillary glands
- Parotids glands
Sub maxillary glands location
Located behind jaws.
produce saliva with amylase and mucous
Parotids glands
Located in front of ears.
Secrete saliva with amylase
Sublingual glands location and production
Below the tongue
Produce saliva
Saliva composition
99.5% water
PH 8 (alkaline) and after loss of CO2 PH 6
NaHCO3(sodium bicarbonate)
digestion in oral cavity steps
selection of food
grinding or mastication
lubrication
digestion
peristalsis and antiperistalsis
waves of circular and longitudinal muscles preeceded by a wave of relaxation squeezing the food down the canal
Antiperistalsis food moves from intestine to stomach and maybe mouth. Causes vomitting.
heart burn or pyrosis
painful burning sensation in chest due to overeating fatty food, caffeine alcoho, smoking
stomach location and appearance
J shaped elastic MUSCULAR BAG
situated BELOW THE DIAPHRAM on the left side of abdominal cavity
cardiac sphincter and pyloric sphincter
ring of muscles located at junction bwtween esophagus and stomach
ring of mucle at junction between stomach and duodenum
3 types of cells and their secretions in stomach [mucosa layer]
All are EXOCRINE except?
- Mucous cells secrete mucus (glycoproteins in nature)
- Pareital cells(oxyntic) secrete HCl.
> maintain PH2
3.Zymogen cells(cheif cells) secrete pepsinogen[inactive protein]
Only endocrine is g cells that secrete gastrin
Stimulates gastric juice prod.
Walls of stomach
Composed of three layers
Outer most layer (sercosa) connective tissue
Middle layer (muscularis) composed of smooth mucles
Inner layer(mucosa) of gastric glands
partially digested food is known as?
and its function
(acidic)Chyme stimulates release of secretions from pancreas, liver and duodenal cells.
small intestine parts
1.Duodenum (first part 20-25cm)
2.Jujenum (second part 2.4 meters)
3.Ileum
role of pancreas (enzyme of pancreatic juice)
enzymes of pancreatic juice;
>Amylase or amylopsin {convert starch to maltose}
>lipase {hydrolyzes fats to fatty acid and glycerol}
>trypsin {splits proteins into polypeptides and peptones}
[it contains sodium bicarbonate which neutralises the chyme coming from stomach]
role of liver in digestion
Detoxification and production of bile.
> secretes bile, which is temporarily stored in gall bladder and released into duodenum
[HAS NO ENZYMES]
> bile is green (due to bile pigments formed from the breakdown of heamoglobin)
if bile pigments dont leave and accumulate in blood, it causes jaundice
Role of Jujenum[and all enzymes+products]
food undigested in duodenum is digested in jujenum and ileum by a group of enzymes.
ENZYMES SUBSTRATE PRODUCT
amino- polypeptide. dipeptide
Peptidase
Erypsin dipeptide amino acid
Lipase fats fatty acids+glycerol
maltase maltose glucose
lactase lactose glucose+galactose
sucrase sucrose glucose+fructose
gastrin hormone in digestion
produced from pyloric region of stomach by G-cells.
stimulus; proteins.
function: secretes pepsinogen and HCl
{more protein=more gastrin secreted=more gastric juice}
secretin hormone in digestion
produced from duodenum by S-cells.
stimulus: entry of acidic chyme in duodenum
Function:
>stimulates bicarbonate-rich pancreatic juice, which helps neutralize the acidic chyme.
> produce *bile rich in bicarbonate,
which further helps in neutralizing the acid in the chyme.
> Inhibit Gastric Secretion
large intestine composition.
Caecum: first part. finger like projections arise known as appendix.
>inflammation of appendix called appendicitus
Colon:divided into four parts.
>ascending colom.travels up the right side of abdomen
>transverse colon:runs across abdomen
>descending colon down the left side of colon
>sigmoid colon: short curve before the rectum.
[Removes water, salt and some nutrients, forming a stool.]
[Diarrhea occurs when water and salts arent absorbed]
[constipation occurs when they are excessively absorbed]
Rectum: defecation reflex
Chemical digestion and mechanical
Chemical involves secretion of enzymes that break chemical bonds and hold food particles together.
Amylase in saliva[oral cavity]
Gastric juice in stomach
Pancreatic juice in small intestine
Mechanical is purely physical such as mastication by teeth for oral cavity
Churning by muscles in stomach
Teeths used for grinding, tearing food in oral cavity (2)
Molars grinddd
Canines tear
Ileum of small intestine function
Nearly all products of digestion takes place here.
Ileum has many inner folds called villi supplied with blood vessels and lymphatic system which make surface area for dissusion of simple sugars and amino acids possible
Functions of components of large intestine
- Caecum: first part. involved in absorbing fluids and salts remained after small intestine digestion and absorption.
- Colon: Absorbs water, electrolytes and vitamins fromm indigestible food matter and converts it into a stool(tatti)
- Rectum stores stool before defacation reflex
Epiglottis
Leaf shaped flap in throat that prevents food from entering windpipe and lungs
