38 Questions
How many kilometers of vessels are present in the human body?
100,000 km
What is the estimated number of blood cells in the human body?
75 million
How many times does the heart beat in a person's lifetime of 80 years?
3.5 billion times
What is the direction of blood flow in the human body?
Unidirectional
What type of circulatory system do humans have?
Closed circulatory system
What is unique about the human heart?
It is divided into right and left sides
What is the purpose of the lymphatic system?
To complete the circuit back to the heart
What is the term for the study of the circulatory system?
Angiology
What type of cells in the heart generate an electrical signal to coordinate contraction?
Autorhythmic cells
What is the volume of blood ejected from the heart during each contraction?
70 mL
What is the formula to calculate cardiac output (CO)?
CO = SV x HR
What system alters heart rate (HR) by changing the depolarization of the autorhythmic cells?
Autonomic nervous system
What is the heart rate (HR) in the example given in the text, where CO = 5.4 L/min?
72 bpm
What is the amount of blood remaining in the heart after each beat, at rest?
65 mL
What percentage of the blood is made up of water?
92%
What is the main function of erythropoietin (EPO)?
To stimulate the production of erythrocytes
What is the purpose of blood doping in athletic performance?
To improve the body's ability to transport O2
What is the main component of the cardiac muscle?
Cardiac muscle
What is the trigger for erythropoietin (EPO) release?
Hypoxia
What is the function of the circulating portion of the blood?
To act as a buffer between the cells and the external environment
What is the percentage of protein in the blood composition?
7%
Where is erythropoietin (EPO) produced?
The kidneys
What is the direction of blood flow in the arterial system?
From arteries to arterioles to capillaries
Why does blood pressure decrease as blood flows away from the heart?
Due to the resistance in the vascular system
What is the significance of the two numbers in a blood pressure reading?
The top number is the systolic pressure and the bottom number is the diastolic pressure
What is the relationship between blood pressure and the distance from the heart?
Blood pressure decreases as you move away from the heart
What is the main reason for the difference in pressure between the arterial and venous systems?
The heart pumps blood more forcefully into the arteries
What is the direction of blood flow in the venous system?
From veins to capillaries to heart
What is the systolic pressure in the arteries when the heart has contracted?
120 mmHg
What is the term for the condition where the blood pressure drops when standing up?
Postural hypotension
Why does blood 'pool' in the feet when standing?
Because the blood is not returning to the heart efficiently
What is the function of the venous valve in the circulatory system?
To prevent backflow of blood
What is the term for the movement of fluid through the capillary walls?
Bulk flow
What is one of the key functions of the lymphatic system?
To return filtered fluid to the circulatory system
What is the term for the pressure in the arteries when the heart is fully relaxed?
Diastolic pressure
What happens when not enough blood is returning to the heart?
The person faints
What is the purpose of the action of venous valves?
To permit flow of blood toward the heart
What is the term for the movement of fluid in both directions on squeezing a fluid-filled tube?
Fluid moving in both directions
Study Notes
Human Circulatory System
- The human circulatory system is a closed system, physically separated from the rest of the body, consisting of vessels and a pump.
- The human heart is divided into right and left sides, making it a "double" circulatory system.
Blood Composition
- Blood is a connective tissue made up of cellular elements suspended in a fluid matrix called plasma.
- It makes up a quarter of the extracellular fluid (ECF) and acts as a buffer between cells and the external environment.
- Blood composition is 92% water, 7% protein, and 1% dissolved organic molecules.
Erythropoiesis
- Erythropoiesis is controlled by the glycoprotein erythropoietin (EPO) and cytokines produced by the kidneys.
- The trigger for EPO release is hypoxia, which relieves reduced oxygen-carrying capacity.
Blood Doping
- Blood doping is used to improve athletic performance by artificially improving the body's ability to transport oxygen to tissues/muscles.
- Three common types of blood doping are blood transfusion, injection of EPO, and injection of synthetic oxygen carriers.
The Heart
- The heart is the "workhorse" of the body, generating pressure to force blood continuously around the body.
- It is composed predominantly of cardiac muscle.
Heart Contraction
- Specialized cells within the heart generate an electrical signal to coordinate contraction.
- This electrical signal depolarizes the membrane, spreading rapidly through the conducting pathway.
Mechanical Events of the Heart
- The heart's mechanical events are controlled by the electrical signal, leading to contraction and relaxation.
Heart Rate
- The heart rate is altered by the autonomic nervous system, changing the depolarization of the autorhythmic cells.
- Cardiac output (CO) is measured by the stroke volume (SV) x heart rate (HR).
Blood Flow
- Blood flows from an area of high to low pressure, driven by blood pressure.
- The arterial system is under high pressure, and the venous system is under low pressure.
Blood Pressure
- Blood pressure is recorded as two numbers: systolic pressure (120 mmHg) and diastolic pressure (80 mmHg).
- Systolic pressure is the pressure in the arteries when the heart has contracted, and diastolic pressure is the pressure in the arteries when the heart is fully relaxed.
Postural Hypotension
- Postural hypotension occurs when standing causes blood to "pool" in the feet, leading to a decrease in blood pressure.
- This can cause fainting, especially in cases where the person does not move their legs.
Capillary Transport
- There are three mechanisms of exchange in capillary transport: movement between endothelium, transcytosis, and bulk flow.
Lymphatic System
- The lymphatic system has three key functions: returning filtered fluid to the circulatory system, fat reabsorption from the gut into circulation, and destroying foreign pathogens.
Explore the pulmonary and systemic circuits of the human circulatory system, and how the heart drives blood flow.
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