Osmoregulation 2

Question 1

epithelial tissues

Answer 1

• form boundry btw animal and environment
• external=skin
• internal=lumen of digestive system and excretory systems

Question 2

specialized epithelial tissues for water and ion regulation found in the…

Answer 2

kidney!

Question 3

animals change flux of water across epithelial tissues by mediating…

Answer 3

permeability of integument

-ie. number of aquaporin proteins open

Question 4

animals reduce water flux on external surface via

Answer 4

• layer of hydrophobic molecues

- in the form of mucus, cuticle with chitin, keratonocytes, or stratum corneum with keratin

Question 5

mucus

Answer 5

• lipoprotein mixture
• primarily found in lungs and GI
• also on skin of semiaquatic animals (frogs, etc)

Question 6

cuticle

Answer 6

• main component is CHITIN (polysaccharide)
• ie arthropod exoskeleton, sometimes used for locomotion attachment
• covers all surfaces, including gut and trachea
• can be many different layers

Question 7

keratinocytes

Answer 7

-terrestrial amphibians and amniotes epidermal layer

Question 8

stratum corneum

Answer 8

• amniotes and tetrapods have this extra layer over keratinocytes
• keratinocytes that have differentiated into corneocytes
• eventually produces the envelope stratum corneum “cornified”

Question 9

epithelial properties for ion movement

Answer 9

• asymmetrical distribution of membrane transporters
• cells interconnected to form impermeable sheet of tissue
• high cell diversity within tissue (specialized for transport or structural support)
• abundant mitochondria

Question 10

asymmetrical distribution of membrane transporters

Answer 10

• solutes selectively transported across membrane depending on needs
• transport proteins stay in place in membrane (do not migrate)

Question 11

cells interconnected forming impermeable sheet of tissue

Answer 11

• little leakage btw cells
• restricts movement of membrane proteins
• 2 paths of transport, transcellular and paracellular

Question 12

transcellular transport vs. paracellular

Answer 12

• aka leaky vs tight
• trans=movement through the cell across membranes (usually via channels or aquaporins)
• para=movement between cells gap junctions

Question 13

digestive epithelia

Answer 13

• water and salts from drinking and food transported across digestive epithelium’s high surface area
• transcellular and paracelluluar transport involved (both directions)
• absorbed water and salts enter blood

Question 14

types of transporters

Answer 14

-ATPases (ie Na+/K+ atpase)
-ion channels (Cl-, K+, Na+)
-electroneutral cotransporters
-electroneutral exchangers
(pg 66-72)

Question 15

abundant mitochondria

Answer 15

-largue supply of ATP for ATPases

Question 16

specialized fish gills

Answer 16

• gills possess ion-pumping cells that cause net uptake of Na and Cl in freshwater and net export in seawater
• gill lamellae composed of mitochondria-rich chloride cells (PNA+)
• pavement cells (PNA-)

Question 17

problems of fish cells

Answer 17

direction of ion transport depends on water salinity, so…

• salinity gradient changes with life history phase
• transporters are “fixed” in membrane
• transporters are expensive to maintain

Question 18

saltwater-freshwater transitions

Answer 18

because salinity forces direction of ion transport, salinity gradients may change during life phase transitions
catadromous=fresh to salt when spawning
anadromous=salt to fresh when spawning
-accomplished by hormone-controlled genetic expression of different ion transport fuctions of epithelia

Question 19

salt glands

Answer 19

• reptiles and seabirds must deal with high salt burden from seawater (direct or food) they ingest, but can’t afford to dilute with water/urine (also problem for desert animals)
• solution: salt glands=near eyes, drain into ducts that empty near nostrils, excreting hyperosmotic solutions of Na and Cl, removing large amounts of salt in small volume of water
• produced by ion pumps and countercurrent multiplier

Question 20

rectal glands

Answer 20

• accessory organ in elasmobranhs
• empties into digestive tract
• active transport of Na and Cl from blood into lumen of gland, similar ion transport to gills and salt glands
• controlled by atrial natriuretic hormone

Question 21

rectal gland pathway

Answer 21

change in osmotic pressure and blood vol=>release of ANH from heart=> vasocative inestinal peptide=>adenylate cyclase=>activates protein kinase a=>activates Cl-channel in membrane for Cl into gland lumen