Theophrastus was considered the "Father of Botany" in the approximate year ____

The heart is a cone-shaped muscular organ located within the ________ of the thorax. its apex rests on the ___________ and its s

Arte-miy333 [17]

The heart is a cone-shaped muscular organ located within the mediastinum of the thorax.

The mediastinum is the space lined with membranous tissue between the lungs. The mediastinum contains not only the heart but also the great vessels (pulmonary artery, aorta, pulmonary veins, and the superior and inferior vena cava), as well as parts of the esophagus and the trachea.

Its apex rests on the diaphragm and its superior margin lies at the level of the 2nd rib.

The apex of the heart is the conical area created by the confluence of the ventricles, but mainly by the left ventricle. It rests on the diaphragm. The superior margin of the heart, also known as the base, lies at the level of the second rib.

Approximately two-thirds of the heart mass is seen to the left of the midsternal border.

This is because to the left of the midsternal border lies the left ventricle which comprises most of the heart mass as the left ventricle is the one responsible for pumping blood throughout the systemic circulation and significant pressure should be overcame; resulting to the physiologic hypertrophy of the left ventricle.

The heart is enclosed in a serosal sac called the pericardium. The loosely fitting double outer layer consists of the outermost fibrous pericardium, lined by the parietal layer of the serous pericardium.

The pericardium is one of three layers of the heart (other ones being the myocardium and the endocardium); and is the outer layer of the heart. The pericardium is composed of two tissues, the fibrous pericardium and the serous pericardium. The pericardium functions to lubricate the movement of the heart by the action of the pericardial fluid.

The heart has four chambers. Relative to the roles of these chambers, the atria are the receiving chambers, whereas the ventricles are the discharging chambers.

The four chambers of the heart are namely the right atrium, right ventricle, left atrium, and the left ventricle. Venous blood goes to the right atrium via the vena cavas then to the right ventricle via the tricuspid valve; then to the pulmonary circulation via the pulmonary artery where it will be oxygenated. From the pulmonary circulation, the left atrium will receive the oxygenated blood via the pulmonary veins then to the left ventricle via the mitral valve where it will be pumped to the systemic circulation via the aorta.

6 0

3 years ago

Which model of replication did the actual results of the Meselson-Stahl experiment support? Explain your answer.

AfilCa [17]

Answer:

Semi-conservative replication

Explanation:

After the double-helix discovery of Watson and Crick, there were three possible models about the DNI replication:

The Conservative model stated that the two strands of DNI together were the template of another new molecule. The final product was the original double-stranded molecule and the new molecule.
The semi-conservative model stated that the original DNI molecule separated into two strands, and each of them served as a template for the synthesis of a new complementary strand. The replication product would be two double-stranded DNA molecules, each carrying an original strand a new one.
The Dispersive moles stated that the replication product would be two molecules made by a mixture of segments of the original and the new molecules.

Meselson and Stahl joined to discover which of the models was the correct one. To do it they used E. coli and Nitrogen isotopes.

First, they extracted DNI from bacteria grown in a medium with N¹⁴ and got its density band by centrifugation.

Then they grew bacteria in a medium with N¹⁵, extracted their DNI molecules, centrifugated them, and got the density band, which was heavier than the firsts ones.

The researchers then transferred bacteria grown in medium with N¹⁵ to a medium with N¹⁴, and they allowed only one replication process to occur. DNI was extracted and centrifugated again, and a new band appeared. This band was an intermediate form between bands of DNI-N¹⁵ and DNI-N¹⁴.

This event eliminated the conservative model. If this model were correct, the expected result would be to get two bands: one corresponding to the density DNI-N¹⁵ and the other corresponding to the density DNI-N¹⁴.

Bacteria grown in a medium with N¹⁵ and then transferred to a medium with N¹⁴ were finally allowed to replicate twice. Their DNI was extracted and centrifugated. The result was two bands: one of them coincided with the intermediate band, and the other one with the DNI-N¹⁴.

This result was conclusive because if the dispersal model were correct, these two bands should not appear, as all the DNI strands would have part of the original molecule.

With this experiment, Meselson and Stahl proved that the correct replication model was the semi-conservative one.

5 0

3 years ago

State the products of anaerobic respiration by yeast and give an application of each in society

QveST [7]

There are two types of respiration namely aerobic and anaerobic respiration. Anaerobic respiration requires oxygen while anaerobic respiration does not require oxygen. The products of anaerobic respiration (also referred to as fermentation) in yeast are carbon iv oxide and ethanol. Anaerobic respiration has a range of applications in the society which includes Brewing process (bear making process) in alcohol industry, bread making process( baking) in baking industry.

8 0

3 years ago

According to scientific evidence, earth’s earliest atmosphere lacked oxygen. Over time, oxygen was added to the atmosphere. Whic

lilavasa [31]

The correct answer is A

hope this helps !

7 0

3 years ago

Which of the following is an example of work being done on an object?

mars1129 [50]

Option B. A man pushes a couch across the room is the answer.

8 0

2 years ago

Read 2 more answers

Theophrastus was considered the "Father of Botany" in the approximate year _____.