topic 6 - human physiology Flashcards
what are the two groups of organs that make up the digestive system?
alimentary canal
accessory organs
what is the alimentary canal
organs through which food actually passes (esophagus, stomach, small + large intestine)
what are the accessory organs?
aid in digestion, but do not actually transfer food (salivary glands, pancreas, liver, gall bladder)
what is the esophagus + what does it do
hollow tube connecting the oral cavity to the stomach
food is mixed with saliva then is moved in abolus via the action of peristalsis
what is a bolus?
soft mass of chewed food
what is the stomach
temporary storage tank where food is mixed by churning and protein digestion begins
lined by gastric pits that release digestive juices, creating an acidic environment
what is the small intestine
long, highly folded tube where usable food substances are absorbed
duodenum, jejunum, ileum
what is the large intestine
final section of the alimentary canal
water and dissolved minerals are absorbed
purpose of salivary glands?
release saliva to moisten food
saliva contains amylase to initiate starch breakdown
parotid gland, submandibular gland, sublingual gland
purpose of pancreas?
produce a broad spectrum of enzymes that are released into the small intestine via the duodenum
secretes certain hormones (insulin, glucagon) which regular blood sugar concentrates
purpose of liver?
takes the raw materials absorbed by the small intestine and uses them to make key chemicals
purpose of gall bladder?
stores the bile produced by the liver (bile salts are used to emulsify rats)
what are the two types of digestion?
mechanical + chemical
what is mechanical digestion
food is physically broken down into smaller fragments
types of mechanical digestion?
chewing (mouth) - grinding action of teeth
churning (stomach) - muscles physically squeeze and mix the food with strong digestive juices (turns into chyme)
segmentation (small intestine): chyme is moved in both directions by the contraction + relaxation of nonadjacent segments of circular smooth muscle
peristalsis (esophagus): contraction of longitudinal smooth muscle, bolus/food moves unidirectionally
what is chemical digestion?
food is broken down by the action of chemical agents
what is the difference between peristalsis and segmentation?
peristalsis: unididrectional movement along alimentary canal, contraction of sequential longitudinal muscles
segmentation: bidirectional movement within small intestine, contraction of nonsequential circular muscles
types / sites of chemical digestion?
- stomach aicds (low pH environment which denature proteins)
- bile (emulsification of fats into droplets)
- enzymes (catalyze hydrolysis reactions)
why does the pancreas release alkaline compounds (ex. bicarbonate ions)
neutralize stomach acids as they enter the intestine as the intestine lacks the mucous membrane which protects the stomach
what is pancreatic juice made of?
proteases endopeptidases amylase nuclease lipase
enzymatic digestion at the following locations? esophagus stomach liver/gall bladder pancreas small intestine
esophagus:
- salivary amylase (starch – maltose)
stomach:
- proteases (protein -> polypeptides)
- stomach acids (chemical digestion)
liver/gall bladder
- amylase (starch –> maltose)
- lipase (triglycerides –> fatty acids)
- endopeptidase (peptides –> amino acids)
- nuclease (DNA/RNA –> nucleosides)
- bicarbonate ions (neutralize stomach acids)
small intestine
- membrane bound enzymes (ex. maltase)
features of villi?
microvilli (SA: Vol up) rich blood supply single layer epithelium lacteals (absorb lipids) intestinal glands (exocrine) membrane proteins
what organ is responsible for glucose storage
liver
how is glucose stored
glycogen
what organ regulates glucose uptake
pancreas
how does amylase break down starch?
amylose is digested into maltose disaccharides
amylopectin is digested into dextrin chains
what are the four main tissue layers of the small intestine?
serosa - protective outer covering
muscle layer - outer layer of longitudinal muscle, inner of circular muscle
sub mucosa - connective tissue, separates muscle layer from mucosa
mucosa - absorbs material from intestinal lumen
what is the difference between what the small intestine absorbs vs what the large intestine absorbs?
small intestine: usable food substances
large intestine: water + dissolved minerals from indigestible food residues
what features of the epithelial lining of villi optimize its capacity to absorb digested materials?
tight junctions (keep digested fluids separated from tissues, maintian concentration gradient)
microvilli (SA up)
mitochondria (epithelial cells of intestinal villi have a large number of mitochondria for ATP)
pinocytotic vesicles
what is absorption?
movement of fluids or dissolved substances (such as nutrients) across a cellular membrane
absorbed components undergo assimilation within the cell to become fluid/solid parts of an organism
what happens during absorption?
digested food monomers must pass from the lumen into the epithelial lining of the small intestine
what are the different methods of membrane transport required to absorb different nutrients?
secondary active transport (glucose and amino acids are co-transported across the epithelial membrane with sodium ions)
facilitated diffusion (certain monosaccharides, vitamins, and some minerals may be transported by epithelial channel proteins)
osmosis
simple diffusion (hydrophobic materials are capable of freely diffusing across the epithelial membrane)
what is endocytosis? why?
invagination of the plasma membrane to create an internal vesicle containing extracellular material
dissolved materials may be rapidly absorbed en masse via the process of pinocytosis (less time than shuttling via membrane proteins)
summary of sugar absorption method?
glucose/galactose (digestive tract) –> cotransport (Na+) –> monosacchardies (epithelial cells of villi) –> facilitated diffusion –> capillary (vessel)
other sugars –> facilitated diffusion –> monosaccharides –> faciliated diffusion –> capillaries
summary of protein absorption?
amino acids (digestive tract) –> co-transport (Na+) –> amino acids (epithelial cells of villi) –> diffusion –> capillaries (vessel)
peptides (<5 a.a.) –> co-transport (H+) –> amino acids –> diffusion –> capillaries
summary of lipids absorption?
fatty acids –> simple diffusion –> fatty acids –> diffusion –> capillaries
micelles (digestive tract) –> simple diffusion –> triglycerides in chylomicrons (epithelial cells of villi) –> diffusion –> lacteal
who proposed the modern understanding of the circulatory system
william harvey
what were Harvey’s proposals
The major blood vessels (arteries & veins) are connected by a single network
Blood flow is unidirectional (due to the presence of one-way valves)
The heart is a central pump (arteries = from heart ; veins = to heart)
Blood flows continuously and is not consumed by the body
how are arteries and veins connected
capillaries (via arterioles and venules)
why are there two sets of atria and ventricles?
two distinct locations for blood transport
what do the atria act as
reservoirs (blood is collected)
what do the ventricles act as
pumps (expelling the blood)
what is systemic circulation + what side of heart
left side + oxygenated blood around the body
what is pulmonary circulation + what side of heart?
right side + deoxygenated blood to the lungs
what is the function of arteries
convey blood at high pressure from the heart ventricles to the tissues of the body and lungs
