Phy digestive system mod 6

what are the 3 major functions of the digestive system

acquisition, digestion and absorption of nutrients

why are absorbed nutrients important

they provide energy (ATP) and building material for the body

which nutrients provide the most energy per gram

fat (9kcal/g)

how many kcal per gram do carbohydrates provide

4 kcal /g

how many kcal per gram do proteins provide

4 kcal/g

what is digestion

breakdown of food into smaller molecules

what is mechanical digestion

physical breakdown of food

gives examples of mechanical digestion

chewing and stomach mixing

why is mechanical digestion important

increases surface area for enzymes

what is chemical digestion

enzyme breakdown of molecules

what is absorption

movement of nutrients into blood or lymph

list the 4 GI layers

mucosa, submucosa, muscularis externa, serosa

what are the 3 layers of the mucosa

mucous membrane, lamina propria, muscularis mucosae

what cells are found in the mucous membrane

enterocytes, goblet cells, endocrine cells

what do goblet cells secrete

mucus

what does the lamina propria contain

blood vessels, lymphatics, nerves, peyers patches

what is the function of muscularis mucosae

mixes food and increase contact for absorption

what plexus is located in the submucosa

meissner’s plexus

what plexus is in the muscularis externa

myenteric (auerbachs) plexus

what digestion occurs in the mouth

mechanical digestion and carbohydrate digestion

which enzyme begins carbohydrate digestion

salivary amylase

what are the functions of saliva

lubrication, taste, carbohydrate digestion

how does food move through the esophagus

peristalsis

what are the three stomach regions

fundus, body, antrum

which cells produce HCI

parietal cells

what are the functions of HCI

kills microbes, activates pepsin, dissolves food

which cells produce intrinsic factor

parietal cells

why is intrinsic factor important

vitamin b12 absorption

what converts pepsinogen into pepsin

hydrochloric acid (HCI)

what does pepsin digest

proteins

which cells produce mucus

mucous cells

why is mucus important

protects stomach lining from acid

which hormone is released in the stomach

gastrin

what does gastrin do

increases acid secretion and stomach contractions

where dies the most digestion occur

small intestine

where does most absorption occur

small intestine

what does the pancreas release

amylase, proteases, lipase, nucleases, bicarbonate

why is bicarbonate released

neutralizes stomach acid

what do villi do

increases surface area

peptides become what

amino acids

disaccharides become what

monosaccharides

where do carbohydrates enter

blood

where do amino acids enter

blood

where do fats enter

lymph

main function of large intestine

water reabsorption

what else is absorbed in the large intestine

salts

what do intestinal bacteria do

produce vitamins and digest some carbohydrates

function of rectum

stores feces

function of anus

eliminate feces

which organs are accessory digestive organs

salivary glands, liver, gallbladder, pancreas

function of liver

produces bile, bicarbonate, plasma proteins, cholesterol metabolism

function of gallbladder

store and concentrates bile

function of pancreas

produces digestive enzymes and bicarbonate

what is peristalsis

wave like contractions that move food

which muscles produces peristalsis

circular and longitudinal smooth muscle

why is mechanical digestion important if enzymes do chemical digestion

it increases food surface area, allowing enzymes to work more efficiently

why is bicarbonate released into the small intestine

to neutralize acidic chyme from the stomach so pancreatic enzymes can function

why are villi essential

they greatly increase surface area for nutrient absorption

why do fats enter the lymphatic system instead of the blood initially

they are packaged into large particles (chylomicrons) that enter lymph before reaching the blood stream

why is intrinsic factor clinically important

without it, vitamin B12 cannot be absorbed, leading to deficiency