Circulatory Systems Heart And Blood Vessels

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Notes

Circulatory System Overview

The **circulatory system** consists of blood vessels, a pump (heart), and valves to ensure one-way blood flow.
Fish have a **two-chambered heart** and a **single circulation** (blood passes through the heart once per circuit).
Mammals have a **four-chambered heart** and a **double circulation** (blood passes through the heart twice per circuit).
The **right side** of the heart pumps deoxygenated blood to the lungs (**pulmonary circulation**).
The **left side** pumps oxygenated blood to the body (**systemic circulation**).
Double circulation allows blood pressure to be raised after the lungs, supplying cells with oxygen and glucose faster.

The Mammalian Heart

The heart is located in the chest; diagram left corresponds to the body's right side.
The **septum** separates the right and left sides of the heart.
The heart is made of **cardiac muscle** supplied with blood by the **coronary arteries**.
**Atria** receive blood; **ventricles** pump blood out.
**Valves** (tricuspid, bicuspid, semilunar) prevent backflow of blood.
Arteries carry blood **away** from the heart; veins carry blood **towards** the heart.

Heart Function (Extended)

Deoxygenated blood enters the **right atrium** via the **vena cava**.
Blood flows through the **tricuspid valve** into the **right ventricle**.
The right ventricle pumps blood through the **semilunar valve** into the **pulmonary artery** (to lungs).
Oxygenated blood returns to the **left atrium** via the **pulmonary vein**.
Blood passes through the **bicuspid valve** into the **left ventricle**.
The left ventricle (thicker wall) pumps blood through the **aorta** to the body.

Monitoring Heart Activity

Heart activity can be monitored using an **ECG**, measuring **pulse rate**, or listening with a **stethoscope**.
Heart rate is measured in **beats per minute (bpm)**.
During exercise, heart rate **increases** to deliver more oxygen and remove waste.
After exercise, heart rate remains elevated to repay **oxygen debt** and break down **lactic acid**.

Coronary Heart Disease

**Coronary arteries** supply the heart muscle with blood.
**Fatty deposits (plaques)** can partially or completely block coronary arteries.
Partial blockage causes **angina** (chest pain); complete blockage leads to a **heart attack**.
Risk factors include **smoking**, **high cholesterol**, **high blood pressure**, **obesity**, and **lack of exercise**.
Reducing risks: quit smoking, eat less animal fat, exercise regularly.

Blood Vessels: Arteries, Veins, Capillaries

**Arteries** carry blood away from the heart at **high pressure**; have thick muscular walls, elastic fibres, and a narrow lumen.
**Veins** carry blood towards the heart at **low pressure**; have thin walls, a large lumen, and **valves** to prevent backflow.
**Capillaries** have walls **one cell thick** and are 'leaky' to allow diffusion of substances.
Arteries divide into **arterioles**; veins receive blood from **venules**.

Main Blood Vessels (Extended)

**Pulmonary artery** carries deoxygenated blood from heart to lungs.
**Aorta** carries oxygenated blood from heart to body.
**Pulmonary vein** carries oxygenated blood from lungs to heart.
**Vena cava** carries deoxygenated blood from body to heart.

Components of Blood

**Plasma** transports carbon dioxide, nutrients, urea, hormones, and heat.
**Red blood cells** (no nucleus) contain **haemoglobin** to transport oxygen as **oxyhaemoglobin**.
**White blood cells** defend against infection: **phagocytes** engulf pathogens; **lymphocytes** produce antibodies.
**Platelets** are cell fragments involved in **blood clotting** and scab formation.

Cross-sections of an artery, vein, and capillary showing wall thickness and lumen size.

Practice questions

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1.Which blood vessel carries blood away from the heart?
Easy
- AArtery
- BVein
- CCapillary
- DVenule
2.The pulmonary artery carries oxygenated blood.
Easy
True or false?
3.Name the structure that separates the right and left sides of the heart.
Easy
4.Which of the following is a risk factor for coronary heart disease?
Medium
- ARegular exercise
- BLow-fat diet
- CSmoking
- DLow blood pressure
5.Complete the sentence about blood flow through the heart.
Medium
Deoxygenated blood enters the right atrium via $the ____$ .
6.Arrange the following structures in the order that blood flows through them after leaving the left ventricle: aorta, left atrium, left ventricle, pulmonary vein.
Hard
- left ventricle
- aorta
- pulmonary vein
- left atrium
7.Why does the left ventricle have a thicker muscular wall than the right ventricle?
Hard
- AIt pumps blood to the lungs.
- BIt pumps blood to the whole body.
- CIt receives blood from the body.
- DIt has to overcome gravity.
8.Match each blood vessel with its correct description.
Medium
- Artery
- Vein
- Capillary
- Thick muscular walls
- Contains valves
- One cell thick walls

Slides

The Circulatory System

The circulatory system consists of blood vessels, a pump (heart), and valves to ensure one-way flow of blood.
Mammals have a double circulation: blood passes through the heart twice per circuit of the body.
The right side pumps deoxygenated blood to the lungs (pulmonary circulation); the left side pumps oxygenated blood to the body (systemic circulation).
Double circulation allows blood pressure to be raised after the lungs, supplying cells with oxygen and glucose faster.

Why is a double circulatory system advantageous over a single circulatory system?

It allows blood to flow more slowly through the lungs.
It reduces the number of times blood passes through the heart.
It allows blood pressure to be raised after passing through the lungs.
It prevents mixing of oxygenated and deoxygenated blood.

The Mammalian Heart

The heart has four chambers: right atrium, right ventricle, left atrium, left ventricle.
The right side receives deoxygenated blood from the body via the vena cava and pumps it to the lungs via the pulmonary artery.
The left side receives oxygenated blood from the lungs via the pulmonary vein and pumps it to the body via the aorta.
The septum separates the two sides; the heart muscle is supplied by coronary arteries.
Remember: Arteries carry blood Away from the heart.

$The ____$ side of the heart pumps deoxygenated blood to the lungs, while $the ____$ side pumps oxygenated blood to the body.

Blood Vessels: Arteries, Veins and Capillaries

Arteries carry blood away from the heart at high pressure; they have thick muscular walls, elastic fibres, and a narrow lumen.
Veins carry blood towards the heart at low pressure; they have thin walls, a large lumen, and contain valves to prevent backflow.
Capillaries have walls one cell thick and 'leaky' walls to allow diffusion of substances; they carry blood at low pressure within tissues.

Which blood vessel has valves to prevent backflow?

Artery
Vein
Capillary
Arteriole

Main Blood Vessels in the Body

Pulmonary artery: carries deoxygenated blood from heart to lungs.
Pulmonary vein: carries oxygenated blood from lungs to heart.
Aorta: carries oxygenated blood from heart to body.
Vena cava: carries deoxygenated blood from body to heart.

The blood vessel that carries oxygenated blood from the lungs to the heart is $the ____$ .

Coronary Heart Disease

The heart muscle receives blood via the coronary arteries.
Coronary heart disease (CHD) occurs when these arteries become partially or completely blocked by fatty deposits (plaques) mainly formed from cholesterol.
Partial blockage causes angina (chest pain); complete blockage leads to a heart attack.
Risk factors include diet high in animal fats, lack of exercise, smoking, and stress.

Which of these are risk factors for coronary heart disease?

Diet high in animal fats
Regular exercise
Smoking
Low blood pressure

Functioning of the Heart (Extended)

Deoxygenated blood enters right atrium via vena cava, passes through tricuspid valve to right ventricle, then is pumped to lungs via pulmonary artery.
Oxygenated blood returns to left atrium via pulmonary vein, passes through bicuspid valve to left ventricle, then is pumped to body via aorta.
Semilunar valves in the pulmonary artery and aorta prevent backflow.
The left ventricle has thicker walls to generate higher pressure for systemic circulation.

Which chamber of the heart has the thickest muscular wall?

Right atrium
Right ventricle
Left atrium
Left ventricle

Effect of Physical Activity on Heart Rate

During exercise, heart rate increases to deliver more oxygen and glucose to muscles and remove waste products faster.
After exercise, heart rate remains elevated to repay the oxygen debt and break down lactic acid built up from anaerobic respiration.
Heart rate is measured in beats per minute (bpm); it can be monitored via pulse, ECG, or stethoscope.

Why does heart rate remain high for a while after exercise?

To increase blood pressure
To repay the oxygen debt and remove lactic acid
To cool down the body
To reduce breathing rate

Components of Blood

Blood consists of red blood cells, white blood cells, platelets, and plasma.
Red blood cells transport oxygen as oxyhaemoglobin; they have no nucleus and a biconcave disc shape.
White blood cells (phagocytes and lymphocytes) defend against infection.
Platelets are cell fragments involved in blood clotting.
Plasma transports carbon dioxide, nutrients, urea, hormones, and heat.

Which of these are functions of blood?

Transport of oxygen
Defence against pathogens
Production of hormones
Blood clotting

Blood Clotting and White Blood Cells (Extended)

Platelets are involved in blood clotting, forming a scab to prevent blood loss and entry of microorganisms.
Phagocytes engulf and digest pathogens (phagocytosis); they have a multi-lobed nucleus and granular cytoplasm.
Lymphocytes produce antibodies and antitoxins; they have a large round nucleus and clear cytoplasm.

The type of white blood cell that engulfs and digests pathogens is called $a ____$ .

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