Unit 15 Circulatory System 1

vertebrates have the most ____ circulatory system in the animal kingdom

highly evolved

functions of the circulatory system:

• transport respiratory gases, nutrients, metabolic wastes, hormones, and antibodies

• maintain internal homeostasis

• remove pathogenic and toxic materials from the body

• temperature regulation

the vertebrate circulatory has 2 components:

• blood-vascular system

• lymphatic system

blood-vascular system

• consists of heart, blood vessels, and blood

• arteries distribute blood from the heart to tissues

• veins return blood from tissues to the heart

• smaller arteries (arterioles) are joined to small veins (venules) by capillaries

  • capillaries form a dense network within tissues

capillaries are usually about ____ long and scarcely larger than the diameter of a ____

1mm, single red blood cell

physiological exchange between blood and tissues takes place through _____

the thin walls of capillaries

types of capillaries:

• continuous

• fenestrated

• sinusoid

portal system

• in certain places in the body (digestive organs, kidneys), blood that has passed a capillary bed elsewhere enters a second capillary bed before reaching the heart

• vessels between two capillary networks constitute a portal system

the blood-vascular system of vertebrates is a ____ of ducts and is said to be a ____

continuum, closed system

• fluid constituents of the blood leak out of the capillaries and into surrounding tissues and is driven by diffusion, osmosis, and pressure produced by the heart

lymphatic system

• fluids would accumulate in tissues and cause swelling if they were not drained by the lymphatic system

• composed of lymph channels and lymph

• tissue fluids (called lymph) enter lymphatic channels

• it then passes into larger lymphatic vessels until discharged into the venous system at several points

lymphatic capillaries in the gut are called ____

lacteals

• absorb fat

the heart provides little pressure to drive ____ and none to drive ____

venous blood, lymph

most veins and lymphatic vessels of tetrapods have ____ to prevent backflow

valves

many lower vertebrates also have lymph sinuses, some of which beat weakly as ____

lymph hearts

the circulatory system is the first of all organ systems to become ____

functional during development

part of the ____ layer of the hypomerme just posterior to the pharynx and ventral to the gut forms folds that fuse to form a _____

splanchnic, longitudinal tube

____ are eventually established that contract in sequence

chambers

the embryonic heart has 2 layers:

• 1) internal endocardium - forms lining of the heart

• 2) external epimyocardium

the epimyocardium matures to:

• external epicardium

  • becomes the serous membrane of the heart

• myocardium

  • forms the muscle of the heart

cardiac muscle fibers are ____, ____ have central nuclei and intercalated disks as well as being ____

striated, branched, involuntary

comparative anatomy of the heart

amphioxus

• no heart

• there is a pulsating vessel in the position where the heart evolved in vertebrates

  • homologous

• a sinus venosus, analogous to the first chamber of the craniate heart, is the termination of the venous system and the beginning of arteries

primitive hearts are a _____

single-circuit pump

• blood from the heart goes in a single loop back to the heart

ancestral vertebrate heart

• a nearly straight tube with 4 (some say only 2) chambers, which contract in sequence

in the order in which blood passes through an ancestral vertebrate heart:

• sinus venosus

• atrium

• ventricle

• conus arteriosus

• pumps a single stream of unoxygenated blood forward in the body

comparative anatomy of the heart

ancestral vertebrate heart

a thin walled ____ recieves blood from the great veins, such as the _______, and empties it through a simple sinutrial valve into an atrium

sinus venosus, common cardinal veins

comparative anatomy of the heart

ancestral vertebrate heart

the ____ expels blood through one or more rows of _____ into a large, thick-walled ____

atrium, atrioventricular valves, ventricle

comparative anatomy of the heart

ancestral vertebrate heart

the ____ pumps blood into the conus arteriosus, which is an enlarged ____

ventricle, artery

comparative anatomy of the heart

ancestral vertebrate heart

the conus arteriosus is lined with several rows of cup-shaped ____ that prevent the backflow of blood into the heart

semilunar valves

comparative anatomy of the heart

cyclostomes and fishes

• vary widely, but depart little from the basic ancestral plan

• in fishes, the heart is relatively far forward in front of the pectoral girdle and under the posterior gills

• the sinus venosus ranges from large (most sharks) to small (cyclostomes)

• cyclostomes may have accessory hearts or pumping mechanisms elsewhere in the body

• the hearts of fishes are relatively small because fishes have a small blood volume

  • all blood in fishes is partially oxygenated, the pump (heart) sends blood to the gills for aeration

• the conus arteriosus varies from long (cartilaginous fishes) to virtually absent (cyclostomes, teleosts)

  • when large, it may contain 2-8 pairs of semilunar valves

• the conus prevents back-flow of blood as the ventricles fills

• the ventral aorta exits the heart

comparative anatomy of the heart

lungfish to reptiles: intermediate hearts

• previous hearts pumped a single stream of unoxygenated blood

• the heart of birds and mammals pumps a stream of unoxygenated blood and a completely separate stream of oxygenated blood

• the hearts of dipnoans (lungfish), amphibians, and reptiles is intermediate in that it usually receives both “kinds” of blood, but does not provide complete structural separation of the two streams, thus allowing some mixing

comparative anatomy of the heart

dipnoi (lungfish)

• the atrium is partly divided by an interatrial septum into right and left chambers

• the sinus venosus delivers deoxygenated blood to the right chamber

• pulmonary veins supply oxygenated blood to the left chamber

• the ventricle is only partly divided by a large muscular interventricular septum, but there is very little mixing of blood

• the conus is large and partly divided by a spiral fold (valve)

• most deoxygenated blood goes to the 5th and 6th aortic arches - then to the posterior gills and lungs

• oxygenated blood goes to the 3rd and 4th arches - then to the body

comparative anatomy of the heart

Anura

• 3 chambers

• the atrium is completely divided into right and left chambers

  • right - unoxygenated, left - oxygenated from the lungs

  • a beginning of double circulation

• but, blood from the skin (which has been oxygenated), joins systemic veins, so there is mixing of blood on the right side

• the ventricle is undivided, yet minimal mixing of the 2 streams of blood takes place

• the conus has a spiral valve which sends deoxygenated blood to the lungs and skin and oxygenated blood to the right systemic arch (out of the body)

comparative anatomy of the heart

urodela

• 2 to 3 chambers in the heart

• it is a less effective double-circuit pump because they are less dependent on pulmonary respiration

• the interatrial septum may be lost (regression)

comparative anatomy of the heart

reptiles

• 3 to 4 chambers in the heart

• a completely divided atrium is present

• the ventricle is incompletely divided into dorsal and ventral chambers by a septum

• the conus is unique in that it divides into 3 channels

  • pulmonary trunk

  • right and left trunks

• crocodilians

  • a complete interventricular septum is present - 4 chambered heart

comparative anatomy of the heart

homeotherm heart: double-circuit pump

• adult birds and mammals have complete double circulation

  • a low-pressure pulmonary circuit using the right side

  • a high-pressure systemic circuit using the left side

comparative anatomy of the heart

homeotherms

• sinus venosus

  • vestigial in birds

  • absent in mammals

• atrium

  • completely divided

• ventricle

  • divided

• conus

  • divides into the pulmonary trunk (right ventricle) and a systemic trunk (left ventricle)

• systemic trunk - single

  • birds - loop to the right

  • mammals - loop to the left

comparative anatomy of the heart

birds

• complete double circulation

• no sinus venosus - it is vestigial

• 2 precavas and one post cava enter the right atrium

• elimination of the left aorta - mirror image of mammals

  • the right aorta is maintained

comparative anatomy of the heart

mammals

• elimination of the right aorta (left is retained)

• interatrial and interventricular septa - completely divided

• sinus venosus incorporated into the right side of the adult heart

  • not apparent anymore

• chordae tendinae - cords attached to valves and to papillary muscles

comparative anatomy of the heart

other mammal heart parts

• papillary muscles

• valves

  • atrioventricular

  • semilunar

• trabeculae carnae

summary of cardiac evolution

shape

• ancestral vertebrate - probably straight

• modern vertebrate - folded

summary of cardiac evolution

sinus venosus

• in intermediate hearts - joins the right atrium

• in birds and mammals - merges into the wall of the right atrium and becomes inapparent

summary of cardiac evolution

atrium

• partly divided - dipnoans and salamanders

• completely divided - other tetrapods

summary of cardiac evolution

ventricle

• incomplete ventricular septum - dipnoans

• complete septum - crocodiles, birds, mammals

summary of cardiac evolution

Conus Arteriosus

• partly divided by spiral fold - dipnoans, anurans

• completely divided into 3 trunks - reptiles

  • pulmonary, right systemic, left systemic

• completely divided into 2 trunks - birds, mammals

  • pulmonary, systemic

verterbrate blood consists of blood cells suspended in a fluid called ___

plasma

plasma contains:

• nutrients

• metabolic wastes

• salts

• hormones

• proteins - albumin, globulins, fibrinogen

  • most probbably formed in the liver

• water

_____ : basically a plasma with reduced protein content

lymph

_____: fluid remaining after blood has clotted

serum

types of blood cells:

• erythrocytes: red blood cells

• leucocytes: white blood cells

• thrombocytes: platelets

  • involved in clotting

erythrocytes

• smaller than white blood cells

• flat

• nucleated or non-nucleated - depending on the species

• contain hemoglobin

  • combines with oxygen and carbon dioxide

leukocytes

• less numerable in vertebrates

  • 1% (mammals) to 10% (fishes) versus red blood cells

  • actively move through capillary walls and aggregate at sites of infection or injury

types of leukocytes

• agranular

  • lymphocytes

  • monocytes

• granular

  • basophils

  • neutrophils

  • eosinophils

hemopoiesis

• the process of blood cell formation

• blood cells are short-lived for the most part

hematopoietic stem cells

• the type of cell that is a precursor or immature blood cell

• hematopoietic stem cells are able to differentiate into different types of blood cells

hematopoietic stem cells give rise to 5 different - blast cells (nucleated precursor cells), each of which develops into specific blood cell types:

• 1) proerythroblasts: form mature erythrocytes

• 2) myeloblasts: form mature neutrophils, eosinophils, and basophils

• 3) monoblasts: form mature monocytes

• 4) lymphoblasts: form mature lymphocytes

• 5) megakaryoblasts: form mature platelets

lymph nodes produce:

lymphocytes

the spleen may produce, destroy, or store __

blood cells

• hemal nodes - some animals have small nodules of splenic tissue

lymph nodes:

• usually oval or bean-shaped

• 1-25 mm in length

• scattered throughout the body

• heavily concentrated in areas like the mammary area, axillary area, and groin area

• each has an outer capsule of dense connective tissue

• lymph nodes have an outer cortex

  • where T cells and macrophages are located

  • also in the cortex are B cells

    • this is where B cells proliferate into antibody-creating plasma cells

lymph flows through lymph nodes in only one direction

• it enters the lymph node through afferent lymphatic vessels and exits through efferent lymphatic vessels

• efferent vessels are wider and fewer in number and exit the lymph nodes on one side in a small depression called the hilus