Human Physiology Flashcards
1
Q
digestion in animals
A
- hydra (cnidarians): digestion in gastrovascular cavity - cells of gastrodermis (lining of cavity) secrete digestive enzymes into cavity for extracelular digestion, some specialized nutritive cells have flagella that move food around and some have pseudopods to engulf food particles
- earthworm: long, straight tube, ingests decaying organic matter along with soil - food moves to esophagus from mouth and into crop to be stored, gizzard posterior to crop with thick muscular walls to grind up food with help of sand and soil, rest of digestive tract of intestines where chemical digestion + absorption occur
- grasshopper: also has long tube with crop and gizzard, has specialized mouth parts for tasting, biting, crushing and has gizzard with plates of chitin to grind food, digestive tract also responsible for removing nitrogenous waste (uric acid)
2
Q
digestion in humans
A
- digestive system has 2 functions: digestion (breaking down large food molecules into smaller molecules) and absorption (diffusion of smaller molecules in body’s cells)
- fats →glycerol + fatty acids
- strach →monosaccharides
- nucleic acids → nucleotides
- proteins →amino acids
- vitamins/minerals small enough to be absorbed without being digested
- tract about 9 m long with smooth (involuntary) muscle that pushes food along by **peristalsis
3
Q
mouth
A
- tongue and different types of teeth break down food mechanically
- type of teeth mammal has reflects dietary habits
- 3 different types of teeth in omnivore: incisors for cutting, canines for tearing, molars for grinding
- salivary amylase relased by salivary glands being chemical breakdown of starch
4
Q
esophagus
A
- food directed into esophagus after swallowing
- prevented from going into windpipe by epilglottis (flap of cartilage at back of pharynx)
- no digestion
5
Q
stomach
A
- churns food mechanically and secretes gastric juice to begin digestion of proteins
- lining of stomach contains gastric pits that are lined with 3 cells:
- chief cells secrete pepsinogen, inactive form of pepsin (activated by acid)
- parietal cells secrete hydrochloric acid that keeps pH of gastric juices at 2-3 and activates pepsinogen, also kills microorganisms and break down protein
- third type secretes mucus that protects stomach lining from substances
- contain rennin to help digestion of protein in milk
- lower esophageal sphincter at top of stomach keeps food in stomach from backing up into esophagus and burning
- pyloric sphincter at bottom of stomach keeps food in stomach long enough for digestion
6
Q
small intestine
A
- digestion completed in duodenum
- intestinal enzymes + pancreatic amylases hyrdolyze starch and glycogen into maltose
- bile (made in liver and stored in gallbladder) released into small intestine and acts as emulsifier to break down fats, and creat greater surface area for digestive enzymes
- peptidases (trypsin + chymotrypsis) break down proteins
- nucleic acids hydrolyzed by nucleases and lipases break down fats
- lower part of smal intestine for absorption
- millions of fingerlike projections (villi) absorb nutrients , each villus contains capillaries to absorb amino acids, vitamins, monosaccharides
- lacteal (small vessle of lymphatic system) absorbs fatty acids and glycerol
- each epithelial cell of villus has microscopic cytoplasmic appendages (microvilli) to increase rate of absorption
7
Q
large intestine/colon
A
- 3 main functions: egestion (removal of undigested waste), vitamin production (bacteria symbionts living in colon), removal of excess water’
- last 18-20 cm of gastrointestinal tract called rectum, stores feces until release, opening is anus
8
Q
hormones
A
- released when person sees/smells food or as food moves along gut
- gastrin (produced at stomach wall), stimulates sustained secretion of gastric juice
- secretin (duodenum wall), stimulates pancreas to release bicarbonate to neutralize acid in duodenum
- cholecystokinin (duodenum wall), stimulates pancreas to release pancreatic enzymes and gall bladder to release bile into small intestine
9
Q
gas exchange in animals
A
- diffusion of respiratory gases, oxgyen, carbon dioxide between outside and cells occurs passively by diffusion
- respiratory surfaces thin, moist, large surface areas
- sponges + hydra: occurs over entire surface of organism wherever cells are in contact with environment
- earthworms + flatworms: external respiratory surface as diffusion of O2 and CO2 occurs at skin, oxygen carried by hemoglobin dissolved in blood
- grasshopper + arthropods/crustaceans: internal respiratory surface, air enters body through spiracles and travels through system of tracheal tubes into body where idffusion occurs in sinues/hemocoels (oxygen carried by hemocyanin in arthropods/mollusks)
- aquatic animals: gills to take advantage of countercurrent exchange to maximize diffusion of gases
10
Q
gas exchange in humans
A
- air enters nasal cavity and moistened, warmed, filtered
- air passes through larynx down trachea and bronchi into bronchioles, which end in microscopic air scals (alveoli) where diffusion of respiratory gases occurs
- internal respiratory surface
- diaphragm contracts + lowers, chest cavity expands to make internal pressure lower than atmospheric pressure so air is drawn into lungs by negative pressure
- medulla in brain sets rhythm of breathing + monitors CO2 levels in blood by sensing changes in pH of blood (lowers as higher CO2 concentration in blood)
- chemoreceptors (O2 sensors) located in nodes of neural tissue in aorta + carotid arteries leaving heart
11
Q
hemoglobin
A
- respiratory pigment that carries oxygen in blood
- combine loosely w/ 4 oxygen molecules forming oxyhemoglobin
- must be able to bind with oxygen in lungs and unload in body cells (more tightly it binds = more difficult to unload)
- allosteric molecule (shape change when binding to 1 oxygen, easier to bind with other 3, conformation also sensitive to pH) and exhibits cooperativity
12
Q
transport of carbon dioxide
A
- very little CO2 transported by hemoglobin
- carried in the plasma as part of reversible blood buffering carbonic acid-bicarbonate ion system (maintains blood at constant pH 7.4)
- bicarbonate ion produced in 2 stage reaction: CO2 combines w/ water to form carbonic acid (catalyzed by carbonic acid anhydrase in red blood cells), then carbonic acid dissociates into bicarbonate ion and a proton
- proton given up into plasma to lower blood pH or be taken up by bicarbonate ion to raise blood pH
13
Q
circulation in animals
A
- sponge + hydra: no circulatory systems, all cells direct contact w/ environment so no need
- earthworm: closed circulatory system where blood pumped by heart through arteries/veins/ capillaries, oxygen carried by hemoglobin
- grasshopper: open circulatory system - blood pumped by heart into artery, leaves vessel and seeps through spcaes (sinuses/hemocoels) as it feeds body cells, blood moves back into vein and circulates back to heart (no capillaries, colorless and no oxygen)
14
Q
human circulation
A
- closed circulatory system with arteries, veins, capillaries
- red blood cells, white blood cells, platelets all deveop in bone marrow from multipotent stem cells (keeps dividing to replenish blood cells)
15
Q
plasma
A
- liquid portion of blood
- contains clotting factors, hormones, antibodies, dissolved gases, nutrients, wastes
- maintains proper osmotic potential of blood (300 mosm/L)
