Circulatory System Of The VertebratesPresentation Transcript
Circulatory System of the Vertebrates By : Geonyzl L. Alviola
Multicellular animals do not have most of their cells in contact with the external environment and so have developed circulatory systems to transport nutrients, oxygen, carbon dioxide and metabolic wastes. Components of the circulatory system include
a. blood : a connective tissue of liquid plasma and cells
b. heart : a muscular pump to move the blood
c. blood vessels : arteries, capillaries and veins that deliver blood to all tissues
There are several types of circulatory systems.
1. open circulatory system = (evolved in insects, mollusks and other invertebrates)
= pump blood into a hemocoel with the blood diffusing back to the circulatory system between cells. Blood is pumped by a heart into the body cavities, where tissues are surrounded by the blood.
= The resulting blood flow is sluggish.
Circulatory systems of an insect (top) and mollusc (middle). Images from Purves et al., Life: The Science of Biology , 4th Edition, by Sinauer Associates ( www.sinauer.com ) and WH Freeman ( www.whfreeman.com ), used with permission.
2. closed circulatory system = have the blood closed at all times within vessels of different size and wall thickness. In this type of system, blood is pumped by a heart through vessels, and does not normally fill body cavities.
= Blood flow is not sluggish.
= Hemoglobin causes vertebrate blood to turn red in the presence of oxygen;
= but more importantly hemoglobin molecules in blood cells transport oxygen.
= The human closed circulatory system is sometimes called the cardiovascular system .
= A secondary circulatory system, the lymphatic circulation , collects fluid and cells and returns them to the cardiovascular system.
Vertebrate Circulatory Systems:
transport gases, nutrients, waste products, hormones, heat, & various other materials
consist of heart, arteries , capillaries, & veins
= carry blood away from the heart
= have muscular, elastic walls
= terminate in capillary beds
= have very thin walls (endothelium only)
= are the site of exchange between the blood and body cells
= carry blood back to the heart
= have less muscle in their walls than arteries but the walls are very elastic
= begin at the end of capillary beds
= a muscular pump (cardiac muscle)
= contains a pacemaker to regulate rate but rate can also be influenced by the Autonomic Nervous System
open blood vessels ,
The heart has two chambers separated by a cartilaginous rod. When muscles contract to bend this rod, the volume of each chamber changes; one side expanding to draw in blood and the other contracting to expel blood.
the sinus venosus receives blood & is filled by suction when the ventricle contracts & enlarges the pericardial cavity
the atrium is a thin-walled muscular sac; an A-V valve regulates flow between atrium & ventricle
the ventricle has thick, muscular walls
the conus arteriosus leads into the ventral aorta (and a series of conal valves in the conus arteriosus prevent the backflow of blood)
heart is similar to that of cartilaginous fishes, except a bulbus arteriosus (a muscular extension of the ventral aorta) is present rather than a conus arteriosus (a muscular extension of the ventricle)
which is probably why most of them are
Blood collected from throughout the fish's body enters a thin-walled receiving chamber, the atrium .
As the heart relaxes, the blood passes through a valve into the thick-walled, muscular ventricle .
Contraction of the ventricle forces the
blood into the capillary networks of the
gills where gas exchange occurs.
The blood then passes on to the capillary networks that supply the rest of the body where exchanges with the tissues occur.
Then the blood returns to the atrium.
Lungfish & amphibians - modifications are correlated with the presence of lungs & enable oxygenated blood returning from the lungs to be separated from deoxygenated blood returning from elsewhere
Partial or complete partition within atrium (complete in anurans and some urodeles)
Partial interventricular septum ( lungfish ) or ventricular trabeculae (amphibians) to maintain separation of oxygenated & unoxygenated blood
Formation of a spiral valve in the conus arteriosus of many dipnoans and amphibians. The spiral valve alternately blocks & unblocks the entrances to the left and right pulmonary arches (sending unoxygenated blood to the skin & lungs).
Shortening of ventral aorta, which helps ensure that the oxygenated & unoxygenated block kept separate in the heart moves directly into the appropriate vessels
The Frog Heart
The frog heart has 3 chambers: two atria and a single ventricle .
The atrium receives deoxygenated blood from the blood vessels (veins) that drain the various organs of the body.
The left atrium receives oxygenated blood from the lungs and skin (which also serves as a gas exchange organ in most amphibians).
Both atria empty into the single ventricle.
While this might appear to waste the opportunity to keep oxygenated and deoxygenated bloods separate, the ventricle is divided into narrow chambers that reduce the mixing of the two blood.
So when the ventricle contracts,
oxygenated blood from the left atrium is sent, relatively pure, into the carotid arteries taking blood to the head (and brain);
deoxygenated blood from the right atrium is sent, relatively pure, to the pulmocutaneous arteries taking blood to the skin and lungs where fresh oxygen can be picked up.
Only the blood passing into the aortic arches has been thoroughly mixed, but even so it contains enough oxygen to supply the needs of the rest of the body.
The Lizard Heart
Lizards have a muscular septum which partially divides the ventricle.
When the ventricle contracts, the opening in the septum closes and the ventricle is momentarily divided into two separate chambers.
This prevents mixing of the two bloods.
The left half of the ventricle pumps oxygenated blood (received from the left atrium) to the body.
The right half pumps deoxygenated blood (received from the right atrium) to the lungs.
1. Heart consists of 2 atria & 2 ventricles &, except in adult birds & mammals, a sinus venosus
2 - Complete interatrial septum
3 - Complete interventricular septum only in crocodilians, birds, & mammals; partial septum in other amniotes
Four Chambers: Birds and Mammals
The septum is complete in the hearts of birds and mammals providing two separate circulatory systems:
pulmonary for gas exchange with the environment and
systemic for gas exchange (and all other exchange needs) of the rest of the body.
Arterial channels - supply most tissues with oxygenated blood (but carry deoxygenated blood to respiratory organs). In the basic pattern:
1 - the ventral aorta emerges from heart & passes forward beneath the pharynx
2 - the dorsal aorta (paired above the pharynx) passes caudally above the digestive tract
3 - six pairs of aortic arches connect the ventral aorta with the dorsal aortas
Aortic arches of fishes - general pattern of development of arches in cartilaginous fishes : 1 - Ventral aorta extends forward below pharynx & connects developing aortic arches. The first pair of arches develop first. 2 - Segments of first pair are lost & remaining sections become efferent pseudobranchial arteries 3 - Other pairs of arches (2 - 6) give rise to pre- & posttrematic arteries 4 - Arches 2 - 6 become occluded; dorsal segments = efferent branchial arteries & ventral segments = afferent branchial arteries 5 - Capillary beds develop within nine demibranchs
the same changes convert 6 pairs of embryonic aortic arches into afferent & efferent branchial arteries
arches 1 & 2 are usually lost
the pulmonary artery branches off the 6th aortic arch and supplies the swim bladder (& this is the same way that tetrapod lungs are supplied)
Aortic arches of tetrapods - embryos have 6 pairs of aortic arches:
but the 1st & 2nd arches are temporary & not found in adults
the 3rd aortic arches & the paired dorsal aortas anterior to arch 3 are called the internal carotid arteries
the 4th aortic arches are called the systemic arches
the 5th aortic arch is usually lost
the pulmonary arteries branch off the 6th arches & supply blood to the lungs
Birds & mammals - no mixing of oxygenated & unoxygenated blood; complete interventricular septum + division of ventral aorta into 2 trunks:
Pulmonary trunk that takes blood to the lungs
Aortic trunk that takes blood to the rest of the body
Result of modifications: All blood returning to right side of heart goes to the lungs; blood returning from lungs to the left side of heart goes to systemic circulation.