D. CIRCULATORY SYSTEM
1. Name the general components of the circulatory system.
Heart, blood vessels, blood
2. Review the general function of the circulatory system.
The general function of the circulatory system is for transportation of nutrients, gases, hormones, and waste. It also functions in immunity and temperature regulation.
3. Discuss the ontogeny and phylogeny of this system.
Concerning ontogeny, the developmental history of an organism, the circulatory system is the first system to be functional in development. There is similar embryology and phylogeny in all vertebrates. There is individual variation, however, in the circulatory system.
Concerning phylogeny, or evolutionary development, the systems of fish, amphibians, reptiles, birds and mammals show various stages of evolution. In fish, the system has only one circuit, with the blood being pumped through the capillaries of the gills and on to the capillaries of the body tissues. This is known as “single circulation”. The heart of fish is therefore only a single pump (consisting of two chambers). In amphibians and reptiles “double circulation” is used, however the heart is not always completely separated into two pumps. Amphibians have a three-chambered heart. Birds and mammals show complete separation of the heart into two pumps, for a total of four heart chambers; it is thought that the four-chambered heart of birds evolved independently of that of mammals.
4. Define plasma.
Plasma is the clear, yellowish fluid portion of blood, lymph, or intramuscular fluid in which cells are suspended. It differs from serum in that it contains fibrin and other soluble clotting elements.
5. List the three formed elements in blood and briefly discuss their functions.
Erythrocytes are red blood cells that transport oxygen and carbon dioxide to and from the tissues; for example, hemoglobin that carries oxygen.
Leukocytes are white blood cells that help protect the body from infection and disease by aiding in immunity and antibody production. White blood cells include neutrophils, eosinophils, basophils, lymphocytes, and monocytes
Platelets (thrombocytes) are minute, nonnucleated, disklike cytoplasmic body found in the blood plasma of mammals that function to promote blood clotting.
6. Define hemopoiesis. Name the blood stem cell.
Hemopoiesis is the formation of blood or blood cells in the body. The blood stem cells are called hemocytoblasts.
7. Discuss the development of the heart.
The part of splanchnic layer of hypomere just posterior to pharynx and ventral to gut forms folds that fuse to form longitudinal tube. Four chambers are established that begin to contract in sequence. Embryonic heart is nearly a straight tube having four chambers that contract in sequence and pumps a single stream of unoxygenated blood forward in the body.
8. List the layers of the heart wall.
Endocardium, myocardium, epicardium
9. Name the membranes and cavity around the heart.
The parietal and visceral pericardium and the pericardial cavity
10. List the four heart parts of a gill breathing fish. Describe their single circuit of circulation.
In fish, the system has only one circuit, with the blood being pumped through the capillaries of the gills and on to the capillaries of the body tissues. This is known as “single circulation.” The heart parts include the sinus venosus, the atrium, the ventricle, and the conus arteriosus.
11. Locate the heart valves and explain their purpose.
AV valve – one-way valve between the atrium and ventricle to prevent back flow of blood
Bicuspid valve – found in mammals; composed of two triangular flaps; located between the left atrium and left ventricle and regulates blood flow between these chambers
Tricuspid valve – found in mammals; three-segmented valve of the heart that keeps blood in the right ventricle from flowing back into the right atrium
Semilunar valve – one-way valve between ventricle and conus arteriosus in gill breathing fish to prevent back flow of blood
Spiral valve – found in dipnoans and anurans; attempts to divide conus arteriosus
Pulmonary/aortic valve – semilunar valves with semilunar cusps at the entrance to the pulmonary trunk from the right ventricle and aorta from left ventricle of the heart
12. Define bulbus arteriosus. Explain its function. Which animals possess it?
The bulbus arteriosus is the muscular expansion of ventral aorta to ensure steady blood flow in some fish. It is needed since the teleost conus arteriosus is short.
13. Describe the two-circuit heart of lungfish and amphibians. Address any significant changes in their hearts in comparison to the heart of gill breathing fish.
Lungfish and amphibians have a two-circuit heart. In the first circuit, the blood is pumped to the lungs, where it acquires oxygen. It then returns to the heart and enters the second circuit, going to the rest of the body, eventually returning to the heart. In comparison to gill breathing fish, they possess an interatrial septum, partial or complete, an interventrical septum, partial, and a spiral valve to divide the conus arteriosus.
14. List the heart chambers of the amniote heart.
Heart consists of 2 atria and 2 ventricles
15. Discuss the significance of the sinus venosus. Name the vertebrates that possess it.
The sinus venosus acts as the pacemaker for the heart. It is the first chamber in the heart of fish, amphibians, and reptiles, which receives blood from the veins and contracts to force the blood into the atrium. In birds and mammals, it becomes the sinoatrial node and acts as a pacemaker.
16. Characterize the SA node and name the vertebrates that possess it.
In birds and mammals, the sinus venosus becomes the sinoatrial node and acts as a pacemaker.
17. Depict the partitions and valves between amniote heart chambers.
The interatrial septum completely divides the atrium. The interventricular septum completely divides the ventricle in birds, crocodiles, and mammals. Located between the right atrium and right ventricle is the right atrioventricular (tricuspid) valve. Located between the right ventricle and pulmonary trunk is the pulmonary semilunar valve. Located between the left atrium and left ventricle is the left atrioventricular valve (bicuspid). Located between the left ventricle and aorta is the aortic semilunar valve.
18. Define auricle. Name those animals that have it.
The auricle of the heart is the earlobe-shaped process at the base of the heart and extending from the atria found in mammals only.
19. Trace the circulation through a typical amniote heart.
From body: deoxygenated blood flows through Vena cava (anterior and posterior) enter right atrium, to right ventricle, through pulmonary trunk to right and left pulmonary arteries to capillary beds in lungs
From lungs: oxygenated blood flows through pulmonary veins to left atrium to left ventricle through aorta to tissue capillary beds in body through vena cava to right atrium
20. Describe the basic pattern of arterial distribution. Identify which direction arterial blood travels.
Embryonic pattern is basically the same for all vertebrates. Heart pumps blood forward in ventral aorta (also called the truncus arteriosus). Aortic arches run upward through visceral arches. Dorsal aorta is the principal distributing vessel of body. Blood from anterior aortic arches runs forward in internal carotid arteries. Blood from posterior arches runs posteriorly into dorsal aorta where it is distributed by 3 sets of branches: dorsal branches, lateral branches, ventral branches. Arteries carry blood away from the heart.
21. Discuss the ventral aorta, arches, and circulatory routes in fish, include sharks, teleosts, and lungfish.
In fish, blood flows from heart through ventral aorta through 6 aortic arches past gills (capillaries, oxygen in, carbon dioxide out) and to dorsal aorta. Sharks possess a pseudobranchial artery, the efferent branchial artery of arch 1. In teleosts, the first and second arches are gone. Lungfish develop a pulmonary artery from the sixth aortic arch.
22. Describe the general pattern for tetrapod aortic arches. Distinguish the arches amongst amphibians, reptiles, birds and mammals.
General pattern for tetrapod aortic arches includes six arches developing in embryo with the first and second rapidly regressing. The third arch plus paired dorsal aortae create the internal carotid artery. The fifth aortic arch is not present in most. The sixth arch is the pulmonary artery. The common carotid artery arises from ventral aorta. The external carotid artery arises from common carotid artery. Urodeles have a ductus caroticus present and retain the fifth aortic arch. Anurans have no ductus caroticus present after metamorphosis. Reptiles have two aortic trunks and one pulmonary trunk (subdivisions of conus arteriosus). Birds and mammals have one aortic trunk from the third and fourth aortic arches and one pulmonary trunk from the sixth arch. The right fourth arch remains in birds. The left fourth arch remains in mammals. The subclavian artery in mammals forms from part of the right fourth arch. The ductus arteriosus is only present in the fetus of birds and mammals. For birds and mammals, the carotids are the same as the general pattern.
23. Identify the following arteries and discuss their derivatives:
Common carotid – runs upward in the neck and divides into the external and internal carotid arteries; derived from ventral aorta
External carotid – the branch of the carotid artery that supplies blood to the face and tongue and external parts of the head; derived from common carotid
Internal carotid – the branch of the carotid artery that supplies blood to the brain; derived from the third aortic arch plus paired dorsal aortae
Right subclavian – a part of a major artery of the upper extremities or forelimbs that passes beneath the clavicle; derived from part of the right fourth aortic arch
Pulmonary trunk – an arterial trunk with origin from the right ventricle of the heart, and dividing into the right and left pulmonary arteries, which enter the corresponding lungs and branch with the bronchi; derived from the sixth aortic arch
Aortic trunk – the main trunk of the systemic arteries, carrying blood from the left side of the heart to the arteries of all limbs and organs except the lungs; derived from the third and fourth aortic arches
Ductus arteriosus – a short broad vessel in the fetus that connects the pulmonary artery with the aorta and conducts most of the blood directly from the right ventricle to the aorta bypassing the lungs
Ductus caroticus – a portion of the embryonic dorsal aorta between points of juncture with the third and fourth arch arteries; it disappears early in development
24. Describe the general pattern of the dorsal aorta, including the following branches: visceral branches, lateral visceral branches, and somatic branches.
Dorsal aorta – extends into tail as caudal artery; ventral visceral branches include celiac artery to stomach, liiver and pancreas, mesenteric arteries to rest of gut (small and large intestine); lateral visceral branches go to urogenital organs; dorsal somatic branches to spinal cord, muscles, and skin; subclavian arteries to pectoral appendages as branchial arteries; iliac arteries to pelvic appendages as femoral arteries
25. Characterize the venous blood flow patterns in the vertebrates, including the following streams: cardinal stream, renal portal stream, hepatic portal stream, and lateral abdominal stream.
The venous channels in sharks:
Cardinal streams – sinus venosus receives all blood returning to heart. Most blood enters sinus venosus via Common Cardinals. Blood from head is collected by Anterior Cardinals. Postcardinals receive renal veins & empty into Common Cardinals.
Renal Portal stream – Early in development, some blood from caudal vein continue forward as Subintestinal (drains digestive system); this connection is then lost. During development, afferent renal veins (from old postcardinals) invade kidneys, & old postcardinals near top of kidneys are lost; all blood from tail must now enter kidney capillaries.
Lateral Abdominal stream – LA vein starts at pelvic fin (where it receives iliac vein) & passes along lateral body wall; receives brachial vein, then turns, becomes Subclavian vein, & enters Common Cardinal vein.
Hepatic Portal stream & Hepatic sinuses – Among 1st vessels to appear in vertebrate embryos are Vitelline veins (from yolk sac to heart). One Vitelline vein joins with embryonic Subintestinal vein (that drains digestive system) & becomes the Hepatic Portal System. Between liver & sinus venosus, 2 Vitelline veins are known as Hepatic sinuses.
Venous channels in other fishes are much like those of sharks except:
Cyclostomes have no renal portals
In most bony fishes the lateral abdominals are absent & the pelvic fins are drained by postcardinals
Venous channels of tetrapods – early embryonic venous channels are very similar to those of embryonic sharks. Changes during development include:
Cardinal veins & precavae – embryonic tetrapods have posterior cardinals, anterior cardinals, & common cardinals
Urodeles – posterior cardinals persist between caudal vein & common cardinals in adults
Anurans, most reptiles, & birds – posterior cardinals are lost anterior to kidneys
Mammals – right posterior cardinal persists (azygos); part of left posterior cardinal persists (hemiazygos)
Some mammals (e.g., cats & humans) lose the left precava; the left brachiocephalic carries blood from left side to right precava
Early tetrapod embryos – paired lateral veins (like lateral abdominals of sharks) begin in caudal body wall near hind limbs, continue cranially, receive veins from forelimbs, & empty into cardinal veins or sinus venosus. As development continues:
Amphibians – 2 abdominal veins fuse at midventral line & form ventral abdominal vein. Blood in this vessel goes into liver capillaries & abdominals anterior to liver are lost (so abdominal stream no longer drains anterior limbs).
Reptiles – 2 lateral abdominals do not fuse but still terminate in liver capillaries (so do not drain anterior limbs; see diagram below).
Birds – retain none of their embryonic abdominal stream as adults Mammals – no abdominal stream in adults
Renal Portal system:
Amphibians & some reptiles – acquires a tributary (external iliac vein; not homologous to mammalian external iliac) which carries some blood from the hind limbs to the renal portal vein. This channel provides an alternate route from the hind limbs to the heart. Crocodilians & birds – some blood passing from hind limbs to the renal portal by-passes kidney capillaries, going straight through the kidneys to the postcava (see diagram above) Mammals – renal portal system not present in adults
Hepatic Portal system – similar in all vertebrates; drains stomach, pancreas, intestine, & spleen & terminates in capillaries of liver
26. Describe the following veins:
Internal jugular – the deeper of the two jugular veins in the neck that drain blood from the head, brain, face and neck and convey it toward the heart. Arises from Anterior cardinal vein.
Brachiocephalic – either of a pair of veins in the neck, each formed by the union of the internal jugular and subclavian veins, that join to form the superior vena cava. From Common Cardinal V.
Azygous – one of a system of veins that drain the thoracic and abdominal walls; arises as a continuation of the right ascending lumbar vein and terminates in the superior vena cava From Posterior Cardinal V.
Hemiazygous – a continuation of the left ascending lumbar vein; crosses the midline at the 8th vertebra and empties into the azygos vein From Posterior Cardinal Vein.
Precavae/superior vena cava – carries blood from the head and arms and chest and empties into the right atrium of the heart; formed from the azygos and both brachiocephalic veins. From Common Cardinal V.
Iliac – one of three veins draining the pelvic area
Subclavian – a part of a major vein of the upper extremities or forelimbs that passes beneath the clavicle and is continuous with the axillary vein
Umbilical – a vein that passes through the umbilical cord to the fetus and returns the oxygenated and nutrient blood from the placenta to the fetus
Ductus venosus – a fetal vein that passing through the liver to the inferior vena cava
Round ligament – a fibrous cord resulting from the obliteration of the umbilical vein of the fetus and passing from the navel to the notch in the anterior border of the liver and along the undersurface of that organ
Ligamentum venosum – a cord of tissue connected to the liver that is the vestige of the ductus venosus
Subintestinal – vein that drains the digestive system
Vitelline – any of the veins in a vertebrate embryo that return the blood from the yolk sac to the heart or later to the portal vein and in mammals have their function of bringing nutriment to the embryo superseded early by that of the umbilical vein
Inferior Vena Cava (postcava) – a large vein formed by the union of the two common iliac veins that receives blood from the lower limbs and the pelvic and abdominal viscera and empties into the right atrium of the heart. From Posterior Cardinal Vein.
27. Define portal and trunk as they relate to circulation.
Portal – vein that begins and ends in a capillary bed
Trunk – the main stem of a blood vessel apart from the branches-Subdivision of conus arteriosus. An Artery.
28. Trace the blood flow from the right atrium and back to the right atrium in a mammalian fetus.
The contents of the right atrium (which consist of some well oxygenated blood from the posterior vena cava and poorly oxygenated blood returning from the head and forelimbs via the anterior vena cava) enter the right ventricle and are expelled from the heart via the pulmonary artery. The lungs are bypassed by the ductus arteriosus, a shunt linking the pulmonary artery and the aorta, and the foramen ovale of the interatrial septum. The convergence of the poorly oxygenated pulmonary blood and the well-oxygenated aortic blood occurs after the main supply to the head and forelimbs have branched off the aortic arch. This ensures that the blood richest in oxygen reaches the developing brain. The abdominal aorta supplies the rest of the body and gives off two umbilical arteries (branches of the internal iliac arteries) which carry poorly oxygenated blood back to the placenta. The umbilical vein carries re-oxygenated fetal blood from the placenta back to the body cavity and to the liver. From the liver the oxygenated blood is carried through the ductus venosus to the posterior vena cava. Now oxygenated blood and deoxygenated blood are mixed and carried back to the right atrium.