Lab 3 - The Heart

Question 1

sheep and human hearts differ mainly by the shape of their…

Answer 1

atria

Question 2

how does the vena cava in a sheep differ to that of a human

Answer 2

3 major branches - L anterior, R anterior and a posterior vena cava

Question 3

head-end of a human/sheep =

Answer 3

cranial

Question 4

bottom end of a human/sheep =

Answer 4

caudal

Question 5

the caudal end of a sheep is also known as the…

Answer 5

posterior

Question 6

how do you know that you are looking at the ventral view of the heart?

Answer 6

• auricles will be pointed towards you
• ligamentum arteriosum visible
• curved

Question 7

the interventricular sulcus marks the position of…

Answer 7

the septum and the course of one of the coronary arteries and a cardiac vein

Question 8

apex formed by which ventricle?

Answer 8

left ventricle

Question 9

which great artery is visible with no disection

Answer 9

the pulmonary trunk

Question 10

how do you know that you are looking at the dorsal view of the heart?

Answer 10

• flat surface

- vena cava clearly visible

Question 11

name of the fibrous bridge between the pulmonary trunk and the aorta

Answer 11

ligamentum arteriosum

Question 12

name of the first branch of the aorta

Answer 12

brachiocephalic artery

Question 13

if you removed the atria and large arteries and you looked down at the four openings, which opening would be the most ventral? what would emerge in the centre? would the ventricles be more ventral or dorsal?

Answer 13

Pulmonary trunk is the most ventral.
Aorta would arise in the centre.
The ventricles are towards the dorsal side

Question 14

How can you differentiate the auricle from the atrium?

Answer 14

auricle has an irregular internal surface of trabeculae whereas the main atrium is smooth. Different origins in the developing embryo.

Question 15

trabeculae

Answer 15

rods of muscle fibres which cross over and weave around each other

Question 16

moderator band

Answer 16

• slender, muscular bridge which traverses the right ventricle.
• no mechanical function.
• contains purkinje fibres for conduction.

Question 17

chordae tendineae when mitral valve is open and closed

Answer 17

loose when mitral valve is opened

tight when mitral valve is closed

Question 18

how many coronary artery openings? where are they found?

Answer 18

2 openings found in the aorta, just inside the aortic valve flaps

Question 19

where do the cardiac veins return their blood

Answer 19

via tiny perforations in the wall of the small left anterior vena cava

Question 20

coronary ostia

Answer 20

openings to the coronary arteries

Question 21

which structure allows blood to cross from the right to the left atrium in the sheep fetus?

Answer 21

foramen ovale

Question 22

fossa ovalis

Answer 22

• translucent membrane ,which covers the hole in the atrial septum, in the the adult sheep
• found in the posterior vena cava

Question 23

relative wall thickness:
RV
LV
RA
LA

Answer 23

relative wall thickness:
RV = MEDIUM
LV = THICK
RA = THIN
LA = THIN

Question 24

when do the atria fill with blood?

Answer 24

during ventricular systole and isovolumetric relaxation

Question 25

closure of the ________ and _________ valves causes the first heart sound ("____"). closure of the ________ and _________ valves causes the second heart sound ("____")

Answer 25

closure of the _mitral_ and _tricuspid_ valves causes the first heart sound ("_lub_"). closure of the _aortic_ and _pulmonary_ valves causes the second heart sound ("_dub_")

Question 26

when are all four heart valves closed

Answer 26

- isovolumetric contraction | - isovolumetric relaxation

Question 27

max and min pressure in the left ventricle

Answer 27

``` max = 120mmHg min = 5mmHg ```

Question 28

rupture of papillary muscle

Answer 28

- caused by myocardial infarction | - valve collapses and blood leaks onto atrium

Question 29

which side of the heart is the flap covering the foramen ovale

Answer 29

left

Question 30

the ligamentum arteriosum is a remnant of a large fetal vessel called the _____ _______. This vessel carried blood from the ________ ______ to the ______.

Answer 30

the ligamentum arteriosum is a remnant of a large fetal vessel called the _ductus_ _arteriosus_. This vessel carried blood from the _pulmonary_ _trunk_ to the _aorta_.

Question 31

before birth (prenatal) th luns are filled with ______ ____ which ________ their resistance. This is why only ___ of blood from the RV travels to the lungs.

Answer 31

before birth (prenatal) th luns are filled with _amniotic_ _fluid_ which _increases_ their resistance. This is why only _10%_ of blood from the RV travels to the lungs.

Question 32

prenatal aorta carries ________ blood.

Answer 32

mixed. | deoxygenated returning from the lungs and oxygenated coming from the RA (via the foramen ovale)

Question 33

at birth the foramen ovale closes because... (5 steps)

Answer 33

1. resistance in the lungs decrease when they fill with air 2. leads to increased volume returning to the LA 3. pressure in LA becomes greater than RA 4. flap valve closes 5. becomes sealed in place by growth of connective tissue = FOSSA OVALIS

Question 34

postnatal, the ductus arteriosus closes because...

Answer 34

an increase in oxygen causes smooth muscle to contract and close the vessel, forming the LIGAMNETUM ARTERIOSUM

Question 35

If the ductus arteriosus remained open ("______") after birth the result would be a larger shunt of blood from ______ to _______ ______. In that case, the volume of blood reaching the lungs would be ________ than normal.

Answer 35

If the ductus arteriosus remained open ("_patent_") after birth the result would be a larger shunt of blood from _aorta_ to _pulmonary_ _trunk_. In that case, the volume of blood reaching the lungs would be _larger_ than normal.