chapter 6: human physiology

alimentary canal

organs which food passes through

accessory organs

organs that aid in digestion but do not transfer food

mechanical digestion

food is physically broken into smaller pieces

chewing (mastication)

mechanical digestion where the tongue pushes food around the teeth for grinding and cutting mixing with the saliva to create a bolus

bolus

the mixture of food and saliva

churning

mechanical digestion where the muscular stomach squeezes food while mixing with gastric juices making chyme

chyme

the mixture of gastric juices and food

peristalsis

involuntary movements of longitudinal smooth muscles rhythmically contracting and relaxing along the esophagus in one direction

segmentation

circular and longitudinal muscles dividing and mixing food in both directions

chemical digestion

polymers and macromolecules broken down to be used in the body

gastric juices

acidic juices secreted from the stomach therefore denature proteins

bile

breaks up fat particles

absorption in the small instestine

when food is digested, it moves from the lumen to the epithelial layer of the small intestine and in the circulatory and lymphatic system to be transported throughout the body, this may require several transport mechanisms

passive transport

transport of materials across a membrane without the use of energy

simple diffusion

lipids are non-polar and can freely pass through the epithelial cell membrane down the concentration gradient

facilitated diffusion

fructose and vitamins are hydrophilic and use protein channels to pass through membrane down the concentration gradient

active transport

glucose, amino acids, and mineral ions go through protein pumps using ATP to move molecules against a concentration gradient

endocytosis

antibodies from breast milk, the membrane folds inwards to form a vesicle to absorb larger molecules without digesting them

esophagus

long hollow tube connecting the oral cavity to the stomach where the bolus travels down

stomach

large muscular sac lined with gastric pits that release acidic juices where food is mixed by churning

small intestine

long, folded tube where usable nutrients are absorbed; consists of three sections: duodenum, jejunum, and ileum

large intestine

the last section of the alimentary canal, absorption of water and dissolved materials, consists of ascending, transverse, descending, sigmoidal colon, and rectum

salivary glands

glands that release saliva that moistens the food and releases amylase to initiate starch breakdown, includes the parotid gland, submandibular gland, and sublingual gland

pancreas

- the organ producing different enzymes released in the duodenum part of the small intestine
- secretes different hormones regulating blood sugar concentrations

liver

- the organ that makes key chemicals using the raw materials absorbed by the small intestine
- its roles include detoxification, storage, metabolism, bile production, and haemoglobin breakdown

gal bladder

organ that stores bile produced by the liver

enzymes secreted by the esophagus

salivary amylase (starch to maltose)

enzymes secreted by the stomach

- proteases (protein to polypeptides)
- stomach acids (chemical digestion)

enzymes secreted by the liver/gal bladder

bile salts (breaks up lipids)

enzymes secreted by the pancreas

- amylase (starch to maltose)
- lipase (triglycerides to fatty acids)
- endopeptidase (peptides to amino acids)
- nuclease (DNA/RNA to nucleosides)
- bicarbonate ions (neutralise stomach acids)

enzymes secreted by the small intestine

membrane-bound enzymes (e.g. maltase)

small intestine ileum structure

lumen, epithelial layer, villi (intestinal mucosa), sub-mucosa, circular muscles, longitudinal muscles, serosa

mucosa

a highly folded inner layer which absorbs material through its surface epithelium from the intestinal lumen, contains villi

submucosa

composed of connective tissue separating the muscle layer from the innermost mucosa

serosa

a protective outer covering composed of a layer of cells reinforced by fibrous connective tissue

villi

finger like projections in the small intestine, in the mucosa layer

microvilli

part of the villi structure, ruffling of epithelial membrane further increasing surface area

rich blood supply

part of the villi structure, dense capillary network rapidly transports absorbed products

single layer epithelium

part of the villi structure, minimises diffusion distance between lumen and blood

lacteals

part of the villi structure, absorbs lipids from the intestine into the lymphatic system

intestinal glands

part of the villi structure, exocrine pits (crypts of Lieberkuhn) release digestive juices

membrane proteins

part of the villi structure, facilitates transport of digested materials into epithelial cells

cardiac sphincter

A two way circular muscle located between the esophagus and the stomach prevents the regurgitation of food from the stomach into the esophagus

pyloric sphincter

a one way ring shaped muscle at the bottom of the stomach that regulates out of the stomach to the small intestine

chief cells

cells located in the stomach that help with the release of enzymes such as pepsin that help with the breakdown of proteins

goblet cells

cells located in the intestine lining, help with the secretion of mucus and create a protective mucus layer

william harvey

a greek philsopher that believed that arteries and veins were separate blood networks, veins pumping "natural blood" and arteries pumping "heat"

heart structure

4 chambers, right atrium and ventricle, left atrium and ventricle

arteries structure

- narrow lumen to maintain high blood pressure
\-

arteries function

blood vessels that carry blood away from the heart

left ventricle structure

thick wall because the blood is pumped to the entire body, therefore has to withstand more blood

tight junctions

tight connections between cells that create an impermeable barrier, keeps digestive fluids from tissues and maintains the concentration gradient by ensuring one-way movement

mitochondria

epithelial cells have many mitochondria providing ATP for active transport, is required for primary active transport (against gradient) or secondary active transport (co-transport) or pinocytosis

pinocytotic vesicles

the uptake of fluids and dissolved solutes, these materials will be ingested by breaking and reforming of the membrane hence contained in a vesicle