Comparative Anatomy Notes – Set 10
CIRCULATORY SYSTEM - Chapter 12
- Blood vessels - in embryo have homologies in vessels
- inside pharyngeal arches are aortic arches and all embryos have them
- primitive patches are in shark with afferent and efferent arteries
Arteries - carry blood away from heart
- muscular, elastic fibrous walls
- regulates blood pressure
- terminate in capillary beds
Veins - cant function in blood pressure regulation
- not fibrous or muscular
- carry blood toward heart
Heart - modified blood vessel
- some systems in vertebrate body whose veins don’t go to heart, but drain some organs and
dump blood into other organs = Portal System
3 portal systems found in vert.
1. Hepatic
2. Renal
3. Hypophyseal
- these are all veins
Hepatic Portal System - drains intestine and dump into liver
Renal Portal System - drains tails and dumps into kidneys
Hypophyseal - smallest
- capillaries in hypothalmus that dump into anterior pituitary
Heart
- typical tetrapod blood is pumped from heart to lungs via pulmonary arteries and back to
heart by pulmonary veins
Fish Heart
- tube like heart
- 4 chambers
- sinus venosus, atrium, ventricle, conus arteriosus
- Sinus Venosus - thin walled venous chamber
- recieves blood from large veins returning to heart
- ducts of cuvier
- coronary veins
- hepatic veins
- Atrium - large and thin walled
- dorsal to ventricle
- in situ
- Ventricle - dumps into conus artriosus
- continuous with aorta
- Valves separate these chambers
- sino-atrial node
- sino-ventricular node
- semi-lunar valve
- Conus arteriosus - short in bony fish and amphibians
- not found in adult amniotes
Heart of Lungfish and Amphibians vs. Dogfish
2 notable differences
1. Modification of partial or complete partition with in atrium
- left and right atria
2. Advent of Lungs
- double circulation forms
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- modification in conus arteriosus
- semi-lunar valve becomes modified so as to shunt into pulmonary vessels,
deoxygenated blood
= spiral valve - modified semi lunar valve
- allows blood to go to lungs
- structure of frog heart
- most deoxygenated blood goes to lungs
- little blood mixes with in ventricle
- spiral valve directs oxygenated blood entering ventricle from left atrium into other
channels or vessels
- conus is more prominent in anurans than in tailed salamanders
- conus is also called truncus arteriosus
- is also called bulbus cordis
- salamander heart
- bulbus arteriosus - this is a muscular swelling of ventral aorta
- smooth muscle not cardiac
- from generalized fish heart, get partitions ----lung fish
- Urodela - right and left atrium
- sinus venosus dumps into RA
- pulmonary veins leave LV
- one ventricle
- after conus and ventral aorta are vessels
- bird is now pulled away and placed with reptiles in a cleidistic digagram
- reptilian heart is unusual
Amniotes - exhibit 2 atria and 2 ventricles
- birds and mammals
- 2 ventricles are completely seperated from each other
- 2 atria and 2 ventricles = 4 chambers
- Sinus venosus - represents a 5th chamber in reptile heart
- birds and mammals exhibit SV during early embryonic life
- doesnt keep pace with development of atria (right)
- it is incorportated into RA
- becomes sino-atrial node
- pacemaker region of heart
- in adult amniote, RA and LA are seperated
- doesnt close until after birth
- hole there is called foramen ovale
- fossa there is called fossa ovalis
Auricle - sometimes used to equal atrium
- in higher vertebrates refers to flap of tissue that allows expansion of atrial chamber
- get more blood
Heart of Mammals and Birds
- blood flow ****
Aortic Arches
- pull out bottom part makes it more ventral
- pull out last three
- basic pattern has 6 aortic arches
- Major Atrioral channels - embryonically seen
1. Ventral aorta emerges from heart and passes forward beneath pharynx
2. Dorsal Aorta, paired anteriorly, passes caudally above digestive tract and pharynx
3. 6 Pairs of AA connects ventral and dorsal aorta
- get modification of AA system
- in Reptiles, get additional arch stuck in there
Aortic Arches
- most Teleost 1st and 2nd disappear
- the dorsal aortae are now individual vessels
2
- become internal carotids
- extensions extend to head
- in lung fish - pulmonary artery develops
- off of arch #6
- they have gills and also posses lungs
- in Tetrapods - have pulmonary artery from 6th arch
- most - arch #5 is lost
- exceptions - terrestrial tailed salamanders
Tetrapods as a whole ex Frog
-arches 1 and 2 disappear
- in addition, dorsal segment between arches 3 and 4 is dropped
- this part may be retained = ductus caroticus
- when this is dropped, arch #3 has common base that extends to internal
carotids
- ventral aorta extension = external carotid
- 3rd arch = carotid arch
- common carotid is at base between 3 and 4
- arch 5 has been lost
- dorsal segment of 6 has been lost
ex. Frog
- arch 4 has no connection anteriorly
= systemic or aortic arch
- arch 6 = pulmonary arch
- adult anuran gives basic pattern of tetrapods
Urodele - have ductus caroticus
- dorsal segment of 6th arch = ductus arteriosus
Reptiles - general
- 1 and 2 disappear
- Ducuts caroticus is lost
- 5 is lost
- ductus arteriosus is lost
- innovation is introduced in heart and dorsal aorta
= 2nd aortic arch
- independent
- arch from left side comes from right side and loops left
- arch from right side does the opposite
- additional aortic arch - 2 arches in reptiles
Heart of Reptile
Turtle - in addition there is internal pocket inside heart
= Cavum venosum
blood flow
- collected from post cava through sinus venosus to precava - venous
blood
- goes to RA
- venous blood goes to cavum venosum
- valve mechanism that shifts back and forth when blood enters
in
- venous blood is diverted to cavum pulmonale (RV)
- pump into pulmonary artery
- goes to lungs
- returning to heart is oxygenated blood through pulmonary veins
to LA
- from LA - oxygenated blood goes to Cavum arteriosum
- goes back to CV - shift skin
- goes to left and right aortic trunk
- other mechanism involved in other reptiles
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Crocadillian
- mechanism for breathing then diving
- lungs arent utilized
- mechanism allows for blood not to be pumped to lungs
- so vessels constrict around RV
- there is a valve between aortic trunks that allows blood to be diverted
= Foramen of Panizza
- more effectively use its blood
- if RV is closed, LV can pump to both arches because of this hole
- one of aortic trunks leads to head
- innovation is not carried
Bird
- right portion is retained and left aortic region is dropped (3, 4, 5,6)
- opposite in mammals
- Birds have a right AA
- mammals have Left AA
Mammals
- 3, 4, 5, 6 are retained embryonically
- in adult mammals, 1 and 2 are dropped
- external, internal carotids and carotid arch
- 4 arch is systemic
- 5 is lost
- dorsal segement of 6 is lost
- embryonically, we retain dorsal segment of 6
= ductus arteriosus
Venous System
- basic pattern - sinus venosus - all blood returns here
- two vessels enter SV
= common cardinals
- have subclavian veins coming in
- drains lateral abdominals and brachials
- blood from tail goes to cardinal or may go to embryonic vessels to go to liver
Shark
- post cardinals has lost a part
- blood from tail must go through kidneys before it goes to post cardinal
= renal portal system
- Major Venous channels
- Cardinals - anterior, posterior, and common
- Renal Portal
- Lateral Abdominals - drains lateral wall of body
- Vitellines - associated with hepatic portal system
- Coronary
2 other characteristics of higher vertebrates
1. Pulmonary
2. Post Cava
- Embryonic shark has basic venous channels
- adult shark is just slightly modified
- shark is a good representative vertebrate
Common Cardinals - direct blood to sinus venosus
- Anterior Cardinals - receives blood from parts of head
- Post Cardinals - receives blood from kidneys
- Renal Portal - from caudal vein
- lateral Abdominals - blood from abd. stream all way back to illiacs
- hepatic veins - associated with liver
- hepatic portal system - drains intestine into liver
- Modifications occur from basic pattern
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ex. Adult Anurans
- post cardinal lost
- new vessel - post cava
- during embryonic development of man, how does post cave form?
- vessels anastomoste
- gives rise to post cava
ex. Turtle - post cava drains kidneys
- lateral abdominals
- retains renal portal system
- lateral abdominals and renal portal are connected by external illiac vein
Bird - 2 precava
- big post cava
- renal portal system still functioning
- begins to divert - either to or not to kidneys
- can go directly to heart
- All mammals, except monotremes, have lost renal portal system
- common cardinals are known as pre-cava - in higher vertebrates
- anterior cardinal veins = internal jugular
- most mammals retain left and right precava
- cat and man retain only right precava
- anterior vena cava
- left doesnt disappear
- portion becomes coronary sinus that dumps into LA
- post. cardinal veins becomes azygous
- remnant of left post cardinal is present
= hemiazygous
- hepatic portal system drains intestine dumping into liver
- found in all vertebrates
Mammalian Fetal Circulation
- Blood Flow
- oxygenation is taking place at placenta
- oxygenated blood is going to fetus through umbilical veins
- veins carry oxygenated blood = umbilical veins
- vein passes through liver and unites with postcava
- oxygenated blood enters heart at RA and has 2 directions to go
1. It can go to RV
2. It can pass through an interatrial apperature
= foramen ovale
- goes to LA
- going to RV 1st - blood is pumped to pulmonary artery
- leads to lungs, but nonfunctional
- oxygenated blood must be diverted away from lungs
= ductus arteriosus - diverts blood from
pulmonary artery
to aorta
- oxygenated blood goes to all parts of body
- eventually blood goes to placenta through umbilical arteries
At birth - placenta shuts down
- umbilical vein collapses
- interatrial apperature close
- flap of skin allows it
- blood no longer goes to LA
- ductus arteriosus closes
- blood not going through this duct
- now deoxygenated blood enters RV to pulmonary arteries to lungs for
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oxygenation
Fossa ovalis -place where interatrial flap closes
- if not closed, you get mixing of blood
- infant becomes discolored
- ductus arteriosus becomes ligamentum arteriosum
- umbilical veins through liver also collapse
= ductus venosus
- this collapses into ligamentum arteriosum
- collapsed umbilical vein can still be seen near falciform ligament
= round ligament of liver
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