Module 7 - The heart

Question 1

Mammalian heart characteristics…?

Answer 1

double circulation pattern (ie. flows from heart -> lungs -> heart -> circulation -> heart
4 chambered
differences exist in: size, shape, position in thoracic cavity
typically located lower ventral part of mediastinum
pericardium fixed to great arteries & cranial vein & attached to sternum
fixation to diaphragm varies between spp.

Question 2

Quadruped heart orientation & shape…?

Answer 2

less pronounced left-sided orientation & more ventrally tilted long axis v bipeds
elongated & apex pointed (mostly)

Question 3

Ruminant heart orientation…?

Answer 3

larger right lung -> displaces 60% heart to left of mid-line

Question 4

Describe the anatomical structure of the elephant heart…?

Answer 4

double-pointed apex
long axis directed ventro-caudally
paired cranial & single caudal vena cava return blood to heart (left cranial vc < right)
ventral wall caudal vc much thicker (10-20mm) than dorsal (2mm)

Question 5

Equine heart characteristics…? including thoroughbred…

Answer 5

located in thoracic cavity
60% lies left of mid-line
most of hearts surface covered by lungs
Thoroughbred - CV system superior due to proportionately larger heart & spleen/unit body mass v other large mammals
HR range 20-240 bpm
splenic RBC reserve -> doubles PCV & oxygen delivery during max. exercise
sig. linear relationship betwee heart size & Timeform rating

Question 6

Avian heart characteristics…?

Answer 6

location - cranial part of thoracoabdominal cavity in close proximity to sternum
no diaphragm present
apex surrounded by liver lobes
SIMILARITY TO MAMMALIAN HEART - 4 chambered, right/left side, each with atrium & ven.
triangular right AV valve more muscular & NO chordae tendinae
ascending aorta curves to right, not left like in mammals

Question 7

Describe the similarities & differences in avian vs mammalian hearts…?

Answer 7

similarities - 4 chambers, left & right side, atrium & ventricles
differences - location (mammals - lower ventral part of mediastinum, avian - cranial part of thoracoabdominal cavity)
no chordae tendinae in right side AV valve of birds
ascending aorta curves to right in birds, to left in mammals
4-6 pulmonary veins in mammals, 2 in chicken
1 cranial vc enters atrium in mammals, vc 2 separate vessels that enter atrium in chickens
higher HR in birds v mammals
tend to be larger v mammals (relative to body size & mass) - necessary for > metabolic rates during flight

Question 8

Characteristics of reptilian hearts…?

Answer 8

located on ventral midline
heart encased in pectoral girdle (lizards)
complexly structured hearts
THREE/3 partially separated ventricular cava
incomplete septum
ventricle acts like single pressure pump perfusing pulmonary & systemic circuits
HR generally lower than mammals & birds
CV system essential for thermoreg.

Question 9

Describe the blood flow thru a reptilian heart…?

Answer 9

precaval, postcaval & hepatic vein -> sinus venosus -> right atrium (diastole) -> cavum venosum (systole). (Deoxy. blood entering right side ventricle does not mix with oxygenated blood from left side due to muscular ridges in ventricle & timing of vent. contractions)
ventricle divided into 3 subchambers (cavum pulmonale, cavum venosum & cavum arteriosum)
Cavum pulmonale doexy. blood -> lungs via pulmonary artery
Cavum venosum -> aortic branches carry ox. blood -> systemic circulation
normal resp. conditions 60% blood -> lungs, 40% -> systemic circulation