Circulatory System Flashcards
Functions of Circulatory System
- efficient distribution of gases and nutrients
- transport hormones and immune cells
- regulation of body temperature
3 main layers to a blood vessel:
- tunica externa (elastic collagen fibers)
- tunica media (smooth muscle)
- tunica intima (simple squamous epithelium)
Order through vein & artery size from the heart.
heart -> elastic artery -> muscular artery -> arteriole -> capillary bed -> venules -> medium-size veins -> large veins
What does an artery have that a vein does not?
- blood away from heart
- narrow lumen
- tunica media thick
- retain shape w/o blood
- more elastic & collagen fibers
- higher blood pressure
What does a vein have that an artery does not?
- blood to heart
- wide lumen
- tunica externa thick
- collapse without blood
What layers do capillaries have?
capillaries are only tunica intima
What are examples of elastic arteries?
- aorta
- pulmonary arteries
- brachiocephalic arteries
Elastic artery:
- high pressure areas (blood just came out)
- 1-2.5 cm in diameter
- elastic fibers in all tunics
- expand and recoil for continuous blood flow
Muscular arteries example
brachial and coronary arteries
Muscular arteries:
- thick tunica media
- elastic fibers in internal and external elastic membranes
Arterioles:
- 3mm - 10um diameter
- vasoconstrict and vasodilate to control blood flow into capillaries
What happens to the tunica media in vasodilation?
tunica media relaxes
What happens to the tunica media in vasoconstriction?
tunic media contracts
What is the outside layer of a capillary?
basal lamina
What does a capillary lack?
tunica externa & media
Why do the capillaries have a thin wall and narrow diameter?
SA:Vol (water hose) - slows down over broad area which allows more time for diffusion
How do RBCs pass through capillaries?
single file (capillaries barely bigger than a single RBC)
3 types of capillaries and locations of each:
- continuous (blood-brain barrier)
- fenestrated (choroid plexus & glomerulus)
- sinusoid (liver)
a- smooth muscle fibers
b- endothelium
c- pre-capillary sphincter
d- true capillaries
e- thoroughfare channel
f- endothelium
Transport in continuous capillaries
- diffusion through membrane (lipid-soluble)
- transport via vesicles or caveola (large)
- have tight junctions & desmosomes
Transport in fenestrated capillaries
movement through fenestrations (water-soluble)
Transport in sinusoidal capillaries
movement through intercellular clefts (water-soluble)
What type of capillaries from left-right:
- continuous
- fenestrated
- sinusoidal
What are arterioles companion vessels?
venules
Where do venules receive blood from?
capillaries
What 2 things help blood to continuously flow to the heart in the veins?
- valves for 1-way flow
- locomotion moves venous blood in addition to pressure
What can happen if there are unhealthy valves in veins?
varicose veins
What are risk factors for varicose veins?
- pregnancy
- constipation
- standing occupations
What veins lack valves?
- thoracic
- abdominal
- breathing=respiratory pump
What depends on the total cross-sectional area?
velocity of blood flow
What are the basics of fish circulatory system?
1-circuit
2- chambered
What is a true chamber?
atrium or ventricle
How did the 4 chambered heart evolve?
it evolved independently in crocs/birds and mammals
What are peritoneal layers?
coelom
Visceral peritoneum
lining organs
Parietal peritoneum
lining abdominal wall
Peritoneal cavity
open space in abdomen
Pleural cavity
open space around lungs
Pericardial cavity
open space around heart
How does single circulation in the fish work?
heart -> gills -> body -> repeat (no lungs)
What are the chambers of a fish heart?
“4” chambers in a series, but only 2 real chambers
What are the “4” fish heart chambers?
- sinus venosus
- atrium
- ventricle
- bulbus arteriosus
What is the sinus venosus?
has sinoatrial node (SA) and is the pacemaker
What is the bulbus arteriosus?
dampens pressure & gives continuous flow (elastic)
Contraction cycles in teleosts (4):
- relax atrium (-) to draw in blood
- atrial contraction closes SA valve - blood goes to ventricle
- atrium relaxes, new blood enter atrium
- ventricular contraction forces blood into bulbus arteriosus (elastic)
What are the 2 amniote heart specializations:
- atria joined in embryo by foramen ovale
- some have separate L&R ventricles (crocodiles, birds, mammals)
What is the remnant of the foramen ovale?
fossa ovale
Who has double circulation?
amniotes (birds, reptiles, mammals)
What is the exception to reptile circulation?
crocodiles
What is the fate of the sinus venosus in reptiles?
the sinus venosus stays the same in reptiles and works as a pacemaker - it is just smaller
What is the fate of the bulbus arteriosus in reptiles?
it becomes the left systemic arch and the pulmonary artery
How many chambers does a reptile have ?
3 (2 atria + 1 ventricle)
What are the 3 ventricular regions of the reptile?
- cavum venosum (O2 poor blood from right atrium)
- cavum pulmonale
- cavum arteriosum (O2 rich blood from left atrium)
Blood flow of the lizard heart (7):
- DO blood enters sinus venosus, then into right atrium
- Left atrium receives O2-rich blood from pulmonary veins
- Blood enters separate ventricle regions
- During contraction, muscular ridge separates blood flow
- Slight asynchrony in contraction
- Cavum arteriosum blood enters systemic circulation
- Cavum venosum blood enters pulmonary artery via cavum pulmonale
What is special about ectotherms circulatory system?
they have lower oxygen needs
How many chambers does a crocodile have?
4 chambered heart (mammal-like)
Foramen of Panizza
sends blood from left ventricle to the left systemic arch
Where does the blood from the ventricles go when a crocodile is on land?
Right ventricle -> most blood goes to lungs - sphincter closes on left systemic arch
Left ventricle -> blood goes through right & left systemic arches
Where does the ventricle blood go when a crocodile is diving?
Right ventricle -> close sphincter on pulmonary artery - blood goes to the body
Left ventricle -> doesn’t send blood through foramen of panizza (because it has O2-poor blood in left systemic arch from right ventricle)
What are the advantages of right to left cardiac shunt?
- saves energy (why pump blood to lungs)
- increased system circulation (gather O2 stored in tissues)
What do diving birds & mammals do instead of shunting?
- bradycardia
- high myoglobin
- anaerobic metabolism in muscles
- shunt (by-pass) blood to brain, not muscles/GI
What are the two mammal cardiac pacemakers?
- sinoatrial (SA) node
- atrioventricular (AV) node
Sinoatrial (SA) node
- sinus venosus remnant
- on right atrium
Atrioventricular (AV) node
- sinus venosus remnant
- conduct SA node signals to ventricles
- “metronome”
- delays signal to ventricles
- in between ventricles
Why does the AV node delay the signal to the ventricles?
so the atria and ventricles don’t contract at the same time
a- SA node
b- AV node
c- Purkinje fibers
What are the pacemaker nodes of the heart muscles made of?
modified cardiac muscle
- nodal cells
- not nervous tissue
How do we change the paces of heart rate?
nervous system (controlled by cardiovascular control center in medulla oblongata)
1. vagus nerve: parasympathetic - decrease heart rate
2. sympathetic cardiac nerves - increase heart rate
What is the fate of the conus arteriosus (bulbus arteriosus in teleosts)?
- aortic arch
- pulmonary trunk
(tubes that carry blood from ventricles)
Mammalian heart specializations:
- trabeculae carneae: reduce ventricular cohesion (open back after relaxation)
- papillary muscles & chordae tendineae (prevent backflow)
What mammals do not have interaction of maternal and fetal circulation via the placenta?
monotremes
What has O2-rich blood in the fetus circulatory system?
umbilical vein
Foramen ovale
sends right atrium blood to left atrium
Ductus arteriosus
shunts blood from pulmonary artery to aorta
What are the 3 changes in circulation at birth?
- foramen ovale -> fossa ovalis
- ductus arteriosus -> ligamentum arteriosum
- umbilical vein -> round ligament in liver
What is the afterbirth?
- placenta
- extra-embryonic membranes
What is Allen’s rule?
colder environment extremities get smaller in homeotherms
Example of Allen’s rule in rabbits?
big - jack rabbit (dissipate body heat)
medium - snowshoe hare
small - arctic hare (keep heat in core)
How do animals thermoregulate in hot & cold?
hot - dissipate body heat
cold - conserve body heat
Countercurrent exchange
heat is transferred from arteries to vein - increased heat exchange since always running towards warmer blood (fish gills and egret legs)
Rete
found in water mammals - preserves core body heat - heat exchange with arteries & veins intermingling - countercurrent
