digestive system Flashcards
what are the organs of the digestive system?
- mouth
- pharynx
- oesophagus
- stomach
- small/large intestines
what are the accessory organs of the digestive system?
- teeth
- tongue
- salivary glands
- gall bladder
- liver
- pancreas
what are the 6 digestive processes?
- ingestion
- propulsion
- mechanical breakdown
- chemical digestion
- absorption
- defaecation
what does ingestion involve?
taking food and water into digestive tract
where does ingestion usually occur?
via the mouth involving the lips and tongue
what does propulsion involve?
moving food through digestive tract
what are two ways of propulsion through the digestive tract?
- swallowing
- peristalsis
what is peristalsis?
alternate waves of muscle contraction and relaxation (involuntary)
what is mechanical breakdown?
physically breaking the food up into smaller fragments so it can be chemically digested
where does mechanical breakdown occur?
mouth, stomach, small intestine
how does the mouth mechanically breakdown food?
chewing and mixing food with saliva
how does the stomach mechanically breakdown food?
churning and mixing with gastric juices
how does the small intestine mechanically breakdown food?
segmentation
what is segmentation in the small intestines?
mixes food with digestive juices aiding nutrient absorption
what occurs in chemical digestion?
enzymes breakdown complex food molecules into their building blocks (monomers)
where does chemical digestion occur?
mouth, stomach, and intestines
what is absorption in digestion?
passage of end products (monomers) from the lumens of the digestive tract into blood or lymph
what is defaecation?
elimination of indigestible substances, in the form of faeces from the body via the anus
what are the four layers of the tissue in the digestive tract?
- lumen
- mucosa
- submucosa
- muscularis externa
- serosa
what structural modifications does the mouth contain?
lined by stratified squamous cells to allow for continual abrasion and protection of underlying tissue
what additional layer of muscle does the stomach have?
oblique layer
what does the additional oblique layer of muscle in the stomach do?
pummels food and forces chyme into small intestines
what does the mucosa indented into the gastric pits of the stomach contain?
goblet, parietal and chief cells
what are three structural modifications of the small intestines?
- circular folds
- villi
- microvilli
what is the simple epithelium rich in in the large intestine and what does this ease the passage of?
goblet cells, ease the passage of faeces and protects from acids and gases
what is the modified mucosa lined by?
stratified, squamous epithelium
why is the modified mucosa continually replaced?
due to abrasion
what are the three salivary glands?
parotid, sublingual and submandibular glands
what does saliva contain?
- mostly water
- mucus
- electrolytes
- digestive enzymes
- antimicrobial proteins
what are functions of saliva?
- mucus lubricated food
- dissolves food chemicals facilitates taste
- enzymes digest carbs
what is the saliva primarily controlled by?
parasympathetic nervous system
what are the digestive functions of the mouth?
- ingestion
- mechanical breakdown (chewing)
- chemical digestion of carbs
- propulsion
what is the digestive functions of the pharynx and oeophagus?
propulsion (peristalsis) of food to the stomach
what does the muscularis externa: circular and longitudinal within the stomach do?
mix, churn and propel food
what do parietal cells in the stomach produce?
hydrochloric acid
what do chief cells in the stomach produce?
pepsinogen
what do goblet cells in the stomach produce?
mucus
what does hydrochloric acid produced by the parietal cells in the stomach do?
activates pepsin, denatures proteins and destroys most bacteria
what is pepsinogen the inactive form of?
pepsin
what does mucus produced from the goblet cells in the stomach do?
protect mucosa from HCl
what are the digestive functions of the stomach?
- mechanical breakdown
- chemical digestion of proteins
- absorption (minor) of fat-soluble chemicals
- propulsion to small intestine
what are the three subdivisions of the small intestines?
- duodenum
- jejunum
- ileum
what does the duodenum subdivision of the small intestine receive?
receives bile and pancreatic juice for chemical digestion
what is the jejunum subdivision of the small intestine the major site of?
mechanical/chemical digestion
when does the ileum subdivision of the small intestine end?
at large intestine
what do circular folds in the small intestine do?
slow movement of chyme, thus increasing nutrient absorption
what do enterocytes in the villi of the small intestine produce?
intestinal juice
what are the digestive functions of the small intestine?
- propulsion
- mechanical breakdown
- chemicall digestion of all four classes: carbs, proteins, fats and nucleic acids
- nutrient absorption
what type o epithelium is the modified mucosa of the large intestine made of?
simple epithelium
what do goblet cells in the large intestine do?
- ease passageway of faeces
- protect the intestinal wall from bacterial acids and gases
what are the digestive functions of the large intestine?
- absorption
- propulsion
is defaecation is parasympathetic or sympathetic reflex?
parasympathetic
what does propulsion in the large intestines involve?
haustral contractions and mass movement
what bacteria digests remaining foods in the large intestine?
enteric bacteria
where does the gall bladder rest?
inferior surface of the liver
what are the dual blood supplies for the liver?
- hepatic artery
- hepatic portal vein
what does the hepatic artery supply to the liver?
oxygenated blood from the abdominal aorta
what does the hepatic portal vein supply to the liver?
nutrient rich blood from small intestine
what are lobules in the liver composed of?
hepatocytes that radiate from a central vein
what is bile produced by in the liver?
hepatocytes
where does bile produced by the hepatocytes in the liver collect and drain into?
bile duct of the portal triad
what are the functions of the liver?
- digestive function-bile production
- haematologic functions synthesis of plasma proteins
- detoxification
- drug and hormone metabolism
- metabolic functions
what are the metabolic functions of the liver?
- removing and storing excess nutrients
- use of amino acids to yield energy
- breakdown of fatty acids for energy
- vitamin and mineral storage
how does the liver correct nutrient deficiencies?
regulate circulating levels of glucose, triglycerides, fatty acids and cholesterol
where is bile stored?
gall bladder
what does bile contain and what do they do?
bile slats and phospholipids which emulsifies fats, increases surface area for digestive enzymes
where is bile reabsorbed and recycled?
ileum
when is bile released?
when chyme enters the duodenum
what are the enzymes produced by the pancreas?
- amylase
- protease
- lipase
- nuclease
what does amylase digest?
carbs
what does proteases digest?
proteins
what does lipase digest?
lipids
what does nuclease digest?
nucleic acids
where is inactivated protease form activated?
within the duodenum
what does the pancreas produce?
- enzymes
- alkaline pancreatic juices
where does carb digestion occur?
mouth and small intestine
what are carbs broken down into?
monosaccharides
what are proteins broken down into?
amino acids
what are lipids broken down into?
fatty acids and glycerol
what are nuclei acids broken down into?
bases, sugar and phosphate ions
where does majority of absorption occur?
small intestine
where does small amounts of absorption occur?
stomach (lipid soluble), large intestine (water, electrolytes and some vitamins)
what does absorption occur through?
epithelial cells
what does the destination of nutrients depend on?
whether nutrient is water or lipid soluble
how are water soluble nutrients transported?
capillary
how are lipid soluble nutrients transported?
lacteal
what is the destination of water soluble nutrients?
liver via hepatic portal vein
what is the destination of lipid soluble nutrients?
lymphatic circulation > bloodstream > liver via hepatic artery
what is metabolism?
the sum total of the chemical reactions occurring occurring in an organism
what is anabolism?
reactions that build larger molecules from smaller ones
what is catabolism?
reactions that breakdown larger molecules into smaller ones
what are the two metabolic states?
- anabolic/absorptive
- catabolic/post-absorptive
when does the anabolic/absorptive state occur?
when nutrients are in abundance (during and for 4hrs after a meal)
when does the catabolic/post-absorptive state occur?
when no food is being digested and body reserves must be broken down to provide nutrients
what is cellular respirationo?
biochemical process that leads to the production of ATP
what are the 3 processes that cellular respiration involves?
- glycolysis
- tricarboxylic acid cycle (Kreb’s or citric cycle)
- electron transport chain
what are foods other than glucose that can be used to produceATP?
- proteins > amino acids
- triglycerides > fatty acids glycerol
- alcohol
what process converts glucose to glycogen?
glycogenesis
what process converts glucose to triglycerides?
lipogenesis
what are excess amino acids converted to?
triglycerides
what is glycogenolysis?
breakdown of glycogen to glucose
what is glucognogenesis?
production of new glucose from non carb source?
what is the anabolic/absorptive state controlled by?
insulin
what is the catabolic/post-absorptive state controlled by?
glucagon
