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CHAPTERS 42 AND 44 (Circulation and Gas Exchange (Ch42) (Blood (made up of…
CHAPTERS 42 AND 44
Circulation and Gas Exchange (Ch42)
Circulatory system
Open circulatory systems
Circulatory fluid: hemolymph bathing the body cells
Arthropods such as grasshoppers, and some molluscs including clams
Heart pumps the hemolymph through the circulatory vessels into interconnected sinuses, spaces surrounding the organs
Hemolymph and body cells exchange gases and other chemicals within the sinuses
Pores have valves that close when the heart contracts
Relaxation of the heart draws hemolymph back in through pores
Body movements squeeze the sinuses, helping circulate the hemolymph
no arteries to increase bp, so there's more blood at low pressure
requires less energy for distributing blood
Closed circulatory system
Circulatory fluid: blood is confined to vessels and is distinct from the interstitial fluid
Annelids (including earthworms), cephalopods (including squids and octopuses) and all vertebrates
Heart(s) pumps blood into large vessels that branch into smaller ones that infiltrate the tissues and organs
Chemical exchange occurs between the blood and the interstitial fluid, between interstitial fluid and body cells
blood remains within a network of vessels and doesn't leave
carries blood at high pressure and delivers blood quickly
suitable for animals with fast metabolism, be able to move, digest and eliminate waste quickly
Single circulation
Blood flows through heart only once for completing one circulation
pulmonary circulation is absent
2 chambered heart
fish
one atrium, one ventricle
the heart draws in deoxygenerated blood in a single atrium and pumps it out of ventricle
Double circulation
three or four chambered heart
having both pumps within a single heart simplifies coordination of the pumping cycles
amphibians, reptiles and mammals
pathways that enable the blood to flow from the heart to lungs and return back to the heart for systematic circulation
right side, heart pumps oxygen-poor blood to the capillary beds of the gas exchange tissues, O2 into blood and CO2 out of blood
left side, heart pumps oxygen-enriched blood from the gas exchange tissues to capillary beds through out the body
following the exchange of O2 and CO2, nutrients and waste products, the oxygen-poor blood returns to the heart
Types of hearts
2-chambered hearts
fish
one atrium, one ventricle
one single loop
blood goes to the gill to get oxygen, then it goes to the body and then goes back to the heart
2 chambers are separated by a valve
3-chambered hearts
amphibians
two atrial and one ventricle
two loops
one loop goes to the lungs and comes back to the heart
one loop goes to the rest of the body
4-chambered hearts
birds and mammals
2 atria, 2 ventricles
double loops
The atria are the two upper chambers that receive blood from the veins
The ventricles are the two lower chambers that pump blood into the arteries.
The heart can be described as two separate pumps, a left pump and a right pump.
arteries, veins, capillaries
Arteries
no valves
blood speed fast
high pressure with thicker wall
from heart to the rest of the body
carry mostly oxygenated blood
Veins
from the rest of the body to heart
carry mostly deoxygenated blood
low pressure with thinner walls
have valves
blood speed slow
capillaries
connect arteries and veins
carry both blood
walls only one cell thick for diffusion
no valves
Blood pressure
Blood pressure is the force that is exerted against arteries when blood flows through
systolic pressure: measures the pressure in the arteries when the heart muscle contracts
diastolic pressure: measures the pressure in the arteries when the heart is at rest
HBP occurs when the artery walls become less elastic, allowing fat to build up against the walls and prevents blood to get through
LBP (hypotension) means that the heart isn’t pumping as much blood to the body as it should, leading to a lack in O2
HBP is dangerous, the heart works harder to pump blood out to the body and helps hardern the arteries, or atherosclerosis, to stroke, kidney disease, and to heart failure.
when bp is recorded, first number is systolic pressure, second is diastolic
bp is measured for an artery in the arm at the same height as the heart
vasoconstriction: process when the smooth muscles in arteriole walls contract, the arterioles narrow
vasodilation: an increase in diameter that causes bp to fall when smooth muscles relax
Lymph circulation
fluid and proteins leak from the blood capillaries into the interstitial fluids
supporting role for cardiovascular and immune system
maintains homeostasis
lymph: watery fluid flows through lymphatic system; recovery fluid
valves in larger lymphatic vessels prevent in the backflow of fluid
lymph nodes: lymph-flitering organs play an important role in body's defense
lymphatic vessels recover leaked fluid and proteins, carrying them to large veins at the base of the neck
when body fights an infection, wbc multiplies rapidly, lymph nodes become swollen and tender
lymphatic system plays a role in harmful immune responses
Blood
made up of red blood cells, white blood cells, plasma, platelets
RBC: carrying oxygen around the body
Plasma: liquid portion, has a lot of nutrients, carrying CO2 as bicarbonate
WBC: fight infection
Platelets: important in blood clotting
Supply of oxygen to tissues (bound to hemoglobin, which is carried in red cells)
Supply of nutrients such as glucose, amino acids, and fatty acids (dissolved in the blood or bound to plasma proteins
plasma transports substances needed by cells and removes wastes and products from cells
Normal blood pressure is considered 120/70
heart attack: is the damage or death of cardiac muscle tissue resulting from blockage of coronary arteries
stroke: death of nervous tissue in the brain due to a lack of O2
hypertension:chronic hbp damages the endothelium that lines the arteries, promoting plaque formation
hypertension: systolic pressure above 140 mm Hg or diastolic pressure above 90 mmHg
55% plasma, 45 cellular elements
Respiratory organs
Respiratory surfaces
cells carrying out gas exchange have a plasma membrane must be in contact with an aqueous solution
movement of O2, and CO2 across respiratory surfaces takes place by diffusion
respiratory surfaces tend to be large and thin
rate of diffusion is proportional to the surface area
some relatively simple animals like sponges, cells in the body is close to the external environment that gases can diffuse
surfaces is moist epithelium that constitutes a respiratory organ
earthworms, and some amphibians and other animals, skin serves as a respiratory organ
network of capillaries below skin facilitates the exchange of gases between circulatory system and environment
Gills (aquatic animals)
outfoldings of the body surface that are suspended in water
total surface area much greater than that of the rest of the body's exterior
ventilation: maintains the partial pressure gradients of O2, CO2 across the gill that are needed for gas exchange
Countercurrent exchange: exchange of a substance/heat between 2 fluids flowing in opposite directions (blood and water)
gill provides a surface where water (dissolve O2) comes into contact with the blood of the fish
diffusion: O2 will flow from water into blood
Tracheal systems in insects
respiratory surfaces are enclosed within the body, exposed to the atmosphere through narrow tubes
network of air tubes that branch throughout the body
largest tube, tracheae, open to the outside
a moist epithelial lining enables gas exchange by diffusion at the tips of the finest branches
branch to form tracheoles that reach every cell
Lungs
lungs are are localized respiratory organs
an infolding of the body surface, subdivided into numerous pockets
circulatory system transports gases between the lungs and the rest of the body
evolved both in organisms with open circulatory system, such as spiders and land snails, and vertebrates
most reptile and all mammals depend on lungs for gas exchange
turtles: lung breathing with gas exchange across moist epithelial surfaces continuous with their mouth or anus
human lung contains millions of alveoli - air sacs clustered at the tips of the tiniest bronchioles
bronchiole: a fine branch of the bronchi that transports air to alveoli
in mammals, air inhaled through the nostrils passes through the pharynx into trachea, bronchi, bronchioles and alveoli
if lungs are present in amphibians, they are super small
Breathing
positive pressure: forces air down the trachea
negative pressure: pulls air into the lungs when rib muscles and diaphragm contract
amphibian ventilates its lungs by positive pressure breathing
birds use a system of air sacs as bellows to keep air flowing through the lungs in one direction
mammals ventilate their lungs by negative pressure
negative breathing: incoming and outcoming air mix, decreasing efficiency of ventilation
rib cage expands/gets smaller as rib muscles contract/relax
diaphragm: most important; a sheet of skeletal muscle that forms the bottom wall of the cavity
inhalation: active, exhalation: passive
diaphragm: inspiration; when it contracts, it flattens out, increasing volume inside the lung
innervation: phrenic nerve
external intercostal: allows ribs to move
internal intercostal: draws the ribs together and depress the rib cage
Osmoregulation and Excretion (Ch44)
Osmosis
Hopoosmotic side: lower solute concentration, higher free water concentration
Net water flows from hypoosmotic side to hyperosmotic side
Water enters and leaves cells by osmosis
Occurs when two solutions separated by a membrane differ in total solute concentration
Hyperosmotic side: higher solute concentration, lower free water concentration
The diffusion of free water across a selectively permeable membrane
Marine vs Freshwater animals
Osmolarity of marine animals is the same as that of seawater, so they face no substantial challenges in water balance
Osmolarity of freshwater animals is higher than that of their surroundings, they face the problem of gaining water by osmosis
Marine: excrete salt ions and small amounts of water in scanty urine from kidneys
Freshwater: excrete salt ions and large amounts of water in dilute urine from kidneys
Freshwater: drink almost no water
Marine: gain of water and salt ions from drinking seawater
Freshwater: osmotic water gain through gills and other parts of body surface
Marine: Osmotic water loss through gills and other parts of body surface
Freshwater: uptake of salt ions by gills
Marine: excretion of salt ions from gills
Nitrogenous wastes
Ammonia
animals need access to lots of water because ammonia can be tolerated only at very low concentrations
many invertebrates, most aquatic animals, including most bony fishes
Urea
mammals, most amphibians, sharks, some bony fishes
Urea is less toxic than ammonia for land animals
urea is the product of an energy-consuming metabolic cycle that combines ammonia with CO2 in the liver
Uric acid
birds and many other reptiles, insects, land snails
ric acid can be excreted as a semisolid paste with very little water loss
Excretory organs
Kidneys
: functions in osmoregulation and excretion; organs for transporting and storing urine
Ureters
: carry urine from kidneys to bladders
Urinary bladder
: receive urine from ureters and store urine
Urethra
: during urination, urine is expelled from the bladder through urethra; in males, this is a path for sperms
Sphincter muscles near the junction of the urethra and bladder regulate urination
Nephron
Bowman's capsule
: Collects the incoming fluid from the glomerular capillaries.
Proximal tubule
Sodium, chloride, water, glucose and amino acids are reabsorbed (removed from the tubules).
Organic acids and bases like bile salts, oxalate and urate are secreted into the proximal tubule.
Loop of Henle
Water is reabsorbed mainly in the descending limb and thin segment of the ascending limb.
Sodium, calcium, chloride, magnesium and potassium are actively reabsorbed in the thick segment of the ascending limb.
Distal tubule
Controls the blood flow through the glomerular capillaries and glomerular filtration of the nephron to which it belongs.
Sodium, potassium and chloride reabsorption.
Collecting tubule
Sodium, potassium and chloride reabsorption.
Hydrogen ion secretion.