Mass Transport In Humans Flashcards
In mammals the heart is a part of the….
Double circulatory system - blood passes through the heart twice
Describe how the blood is carried in the heart starting from the vena carva
1) deoxygenated blood returns from the body in the vena carva and enters the right atrium
2) the blood then passes via an atrio-ventricular valve in the right ventricle and out the semi lunar valve into the pulmonary artery
3) the blood now passes through the lungs and returns to the left atrium via pulmonary vein
4) the blood passes through a second atrium-ventricular valve into the left ventricle and then through the semi-lunar valve into the aorta and then onto the body tissues
When do atrioventricular valves open and close
Open when pressure is greater in atria than ventricles
Close when pressure is greater in the ventricle than the atria
When do semi lunar valves open and close
Open when pressure is greater in the ventricle than arteries pulmonary or aorta
Close when pressure is greater in the arteries then ventricles
How do you calculate cardiac output and what is the unit
CO = SV x HR
Stroke volume = volume of blood expelled from the left ventricle on one cardiac cycle
Heart rate = number of cardiac cycles per minute
Volume per unit time dm3 min-1
What are some CHD risk factors
Age
High cholesterol
Lack of exercise
Smoking
High lipid diet
Stress
Gender
Leads to increased blood pressure and increase blood toxins
Define mass flow
The bulk movement of liquids and gases due to a pressure difference
What is the role of an artery
Transport blood away from the heart to the organ.
Blood is under high pressure. Wall is thick to withstand this pressure
What is the structure of the artery
Endothelial layer:
Layer is one cell thick
Gives a smooth layer which reduces friction and gives smooth flow
Middle layer:
Contains large amount of elastic protein fibres
Allows wall to stretch to stop pressure rising too high
Recoils once blood passes to maintain hydrostatic pressure on the blood
Outer layer:
Made of fibrous protein and gives support and strength. To wall, helping it to resist damage due to the high pressure of the blood inside
Explain how an arteriole can reduce the blood flow into capillaries.
- Muscle contracts;
- Constricts/narrows arteriole/lumen;
Describe how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta.
- Atrium has higher pressure than ventricle (due to filling / contraction);
- Atrioventricular valve opens;
- Ventricle has higher pressure than atrium (due to filling / contraction);
- Atrioventricular valve closes;
- Ventricle has higher pressure than aorta;
Points 1, 3, 5, and 7 must be comparative: eg higher - Semilunar valve opens;
Marks 2, 4, 6, 8 given in the correct sequence can gain 4 marks - Higher pressure in aorta than ventricle (as heart relaxes);
- Semilunar valve closes;
- (Muscle / atrial / ventricular) contraction causes increase in pressure
Describe how the movement of the diaphragm leads to air movement into the lungs
- Diaphragm contracts and flattens.
- Volume of lungs increases.
- Pressure inside the lungs is lower than
atmospheric pressure. - Air moves into the lungs.
Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them.
• Many alveoli/ alveoli walls folded provide a large surface area;
• Many capillaries provide a large surface area (So) fast diffusion;
Alveoli or capillary walls/ epithelium/ lining are thin/ one cell thick / short distance between alveoli and blood;
• Flattened/ squamous epithelium (So) short diffusion distance/ pathway / (So) fast diffusion;
• Ventilation / circulation; So Maintains a diffusion / concentration gradient (So) fast diffusion;
Describe the gross structure of human gas exchange system and how we breathe in and out
- (Across) alveolar epithelium;
- Endothelium of capillary;
Arteries and arterioles take blood away from the heart. Explain how the structures of the walls of arteries and arterioles are related to their functions. (6)
Elastic tissue
1 Elastic tissue stretches under pressure/when heart contracts;
2 Recoils/springs back;
3 Evens out pressure/flow;
Muscle
4 Muscle contracts;
5 Reduces diameter of lumen/vasoconstriction/constricts vessel;
6 Changes flow/pressure;
Epithelium
7 Epithelium smooth;
8 Reduces friction/blood clots/less resistance;
