1. Draw, label and describe the external structure of human heart.
Answer: The human heart is a muscular, cone-shaped organ located in the mediastinum of the thoracic cavity, between the lungs. It is about the size of a fist and weighs approximately 250-350 grams.
External Structure:
Pericardium: The heart is enclosed in a double-layered sac called the pericardium. The outer layer is the fibrous pericardium (tough, protective), and the inner layer is the serous pericardium (parietal and visceral layers). The space between them contains pericardial fluid, which reduces friction. Epicardium: The outermost layer of the heart wall, also known as the visceral pericardium. Myocardium: The middle, thickest layer, composed of cardiac muscle. It is responsible for the pumping action. The left ventricle has the thickest myocardium. Endocardium: The innermost layer, lining the heart chambers and valves. It is smooth to prevent blood clotting. Chambers: The heart has four chambers: two upper atria (right and left) and two lower ventricles (right and left). Coronary Vessels: The coronary arteries and veins supply and drain blood from the heart muscle. Grooves: The coronary sulcus separates atria from ventricles; the anterior interventricular sulcus and posterior interventricular sulcus separate the ventricles.
Diagram Description: (A diagram would show the heart with labels: aorta, pulmonary artery, superior vena cava, inferior vena cava, right atrium, right ventricle, left atrium, left ventricle, coronary arteries, and pericardium.)
Functions: The heart acts as a double pump. The right side pumps deoxygenated blood to the lungs (pulmonary circulation), and the left side pumps oxygenated blood to the body (systemic circulation).
In summary, the external structure of the heart is designed to protect it and facilitate its function as a powerful, rhythmic pump.
2. Describe the flow of blood through human heart as regulated by the valves.
Answer: Blood flow through the human heart is unidirectional, regulated by four valves that prevent backflow.
Pathway:
1. Deoxygenated Blood: Enters the right atrium from the body via the superior and inferior vena cava.
2. Right Atrium to Right Ventricle: Blood flows through the tricuspid valve into the right ventricle. The tricuspid valve prevents backflow into the right atrium during ventricular contraction.
3. Right Ventricle to Lungs: The right ventricle contracts, forcing blood through the pulmonary semilunar valve into the pulmonary artery, which carries blood to the lungs for oxygenation. The pulmonary valve prevents backflow into the right ventricle.
4. Oxygenated Blood: Returns from the lungs via the pulmonary veins to the left atrium.
5. Left Atrium to Left Ventricle: Blood flows through the bicuspid (mitral) valve into the left ventricle. The bicuspid valve prevents backflow into the left atrium.
6. Left Ventricle to Body: The left ventricle contracts, forcing blood through the aortic semilunar valve into the aorta, which distributes blood to the entire body. The aortic valve prevents backflow into the left ventricle.
Valve Regulation:
Atrioventricular Valves (Tricuspid and Bicuspid): Open during diastole (when ventricles relax) to allow filling; close during systole (when ventricles contract) to prevent backflow. Semilunar Valves (Pulmonary and Aortic): Open during systole to allow ejection; close during diastole to prevent backflow.
In summary, the valves ensure that blood flows in one direction, from atria to ventricles to arteries, optimizing circulation.
3. State the phases of heartbeat in man.
Answer: The heartbeat consists of a sequence of phases known as the cardiac cycle, which lasts about 0.8 seconds.
1. Atrial Systole (0.1 sec):
The atria contract, pushing blood into the ventricles. The AV valves are open. The semilunar valves are closed. This completes ventricular filling.
2. Ventricular Systole (0.3 sec):
The ventricles contract. The AV valves close (first heart sound "lub"). The semilunar valves open, and blood is ejected into the aorta and pulmonary artery. The atria are relaxed (atrial diastole).
3. Complete Diastole (0.4 sec):
The ventricles relax. The semilunar valves close (second heart sound "dup"). The AV valves open, allowing blood to flow from the atria into the ventricles. The atria are also relaxed.
Heart Sounds:
S1 ("lub"): Closure of AV valves. S2 ("dup"): Closure of semilunar valves.
In summary, the heartbeat is a coordinated sequence of contraction and relaxation phases that ensure efficient blood pumping.
4. Describe the conducting system of human heart.
Answer: The conducting system of the heart is a network of specialized cardiac muscle cells that initiate and distribute electrical impulses, coordinating the heartbeat.
Components:
1. Sino-atrial (SA) Node: Located in the right atrium. It is the pacemaker, generating impulses spontaneously at 60-100 times per minute.
2. Atrioventricular (AV) Node: Located at the junction of atria and ventricles. It receives impulses from the SA node and delays them by 0.1 seconds, allowing atrial contraction to complete.
3. Bundle of His (AV Bundle): A bundle of fibers that carries impulses from the AV node into the interventricular septum.
4. Right and Left Bundle Branches: The bundle of His divides into right and left branches, carrying impulses down the septum.
5. Purkinje Fibers: Fine fibers that spread throughout the ventricular walls. They conduct impulses rapidly, causing the ventricles to contract almost simultaneously.
Function:
The SA node initiates the heartbeat. The AV node delays the impulse, allowing proper filling. The bundle branches and Purkinje fibers distribute the impulse to the ventricles. This ensures coordinated contraction of atria and ventricles.
Regulation: The autonomic nervous system (sympathetic and parasympathetic) can modify the rate set by the SA node.
In summary, the conducting system ensures the heart beats rhythmically and efficiently.
5. Explain electrocardiogram with the help of diagram.
Answer: An electrocardiogram (ECG or EKG) is a recording of the electrical activity of the heart over time. It is a valuable diagnostic tool.
Waves of ECG:
P Wave: Represents atrial depolarization (contraction). It is a small, upward deflection. QRS Complex: Represents ventricular depolarization (contraction). It consists of a small downward Q, a tall upward R, and a downward S wave. It is the largest wave. T Wave: Represents ventricular repolarization (relaxation). It is a rounded, upward deflection.
Intervals:
PR Interval: Time from the start of the P wave to the start of the QRS complex. It reflects the delay at the AV node. QT Interval: Time from the start of the QRS complex to the end of the T wave. It represents the duration of ventricular systole.
Diagram Description: (A diagram would show a typical ECG tracing with P, Q, R, S, T waves labeled.)
Clinical Significance:
Diagnose arrhythmias, heart attacks, and other cardiac conditions. Detect electrolyte imbalances. Monitor the effects of drugs.
In summary, the ECG is a graphical representation of the heart's electrical activity, essential for diagnosing heart conditions.
6. Describe the structure of blood vessels in man.
Answer: Blood vessels are tubular structures that carry blood throughout the body. There are three main types: arteries, veins, and capillaries.
1. Arteries:
Structure: Thick, muscular, elastic walls. The tunica media is thick and contains smooth muscle and elastic fibers. The tunica externa is made of connective tissue. The tunica intima is the inner lining. Function: Carry blood away from the heart. They withstand high pressure. Arterioles are smaller arteries that regulate blood flow to capillaries.
2. Veins:
Structure: Thinner walls compared to arteries. The tunica media is thin. They have valves to prevent backflow. The tunica externa is well-developed. Function: Carry blood toward the heart. They operate under low pressure. Venules are small veins that collect blood from capillaries.
3. Capillaries:
Structure: Microscopic vessels with walls only one cell thick (endothelium). They form networks called capillary beds. Function: Site of exchange of gases, nutrients, and waste between blood and tissues. Their thin walls and large surface area facilitate exchange.
Differences:
Arteries have thicker walls, narrower lumens, and no valves. Veins have thinner walls, wider lumens, and valves. Capillaries are the smallest and most numerous.
In summary, the structure of blood vessels is adapted to their specific functions in the circulatory system.
7. What is the role of precapillary sphincter?
Answer: The precapillary sphincter is a band of smooth muscle that surrounds the entrance to a capillary bed. Its role is to regulate blood flow into the capillaries.
Function:
Vasoconstriction: When the sphincter contracts, it closes the entrance to the capillary, reducing blood flow to that capillary bed. Vasodilation: When it relaxes, blood flows freely into the capillary bed.
Regulation:
The sphincters respond to local metabolic needs. For example, in active tissues, low oxygen and high carbon dioxide levels cause the sphincters to relax, increasing blood flow to meet demand. They also respond to hormones and nerve signals.
Importance:
They ensure that blood is directed to tissues that need it most. They help regulate blood pressure and distribution. They prevent overperfusion of inactive tissues.
In summary, precapillary sphincters are crucial for local control of blood flow and tissue perfusion.
8. Describe pulmonary circulation and systemic circulation.
Answer: The circulatory system is divided into two circuits: pulmonary and systemic.
Pulmonary Circulation:
Function: Carries deoxygenated blood from the heart to the lungs and returns oxygenated blood to the heart. Pathway: Right atrium [source symbol unavailable] Right ventricle [source symbol unavailable] Pulmonary artery [source symbol unavailable] Lungs [source symbol unavailable] Pulmonary veins [source symbol unavailable] Left atrium. Characteristics: Low pressure, short circuit. It allows for gas exchange in the lungs.
Systemic Circulation:
Function: Carries oxygenated blood from the heart to the body tissues and returns deoxygenated blood to the heart. Pathway: Left atrium [source symbol unavailable] Left ventricle [source symbol unavailable] Aorta [source symbol unavailable] Body tissues [source symbol unavailable] Superior/Inferior vena cava [source symbol unavailable] Right atrium. Characteristics: High pressure, long circuit. It delivers oxygen and nutrients to tissues and removes waste products.
Coordination: The two circuits are connected in series. The output of one becomes the input of the other. This ensures that blood is continuously oxygenated and circulated.
In summary, pulmonary and systemic circulations work together to maintain oxygen and nutrient supply to the body and remove waste products.
9. Describe hepatic portal system.
Answer: The hepatic portal system is a network of veins that carries blood from the digestive organs to the liver before it returns to the heart.
Structure:
Hepatic Portal Vein: Formed by the union of the superior mesenteric vein and splenic vein. It also receives blood from the gastric and cystic veins. Capillaries: The portal vein branches into capillaries in the liver (hepatic sinusoids). Hepatic Veins: Blood from the liver drains into the hepatic veins, which empty into the inferior vena cava.
Function:
Nutrient Processing: Blood rich in nutrients (glucose, amino acids, vitamins) from the intestines is processed by the liver. The liver stores excess glucose as glycogen, synthesizes proteins, and detoxifies harmful substances. Detoxification: The liver removes toxins, drugs, and bacteria from the blood before it reaches the general circulation. Storage: The liver stores vitamins, iron, and glycogen.
Significance: The hepatic portal system ensures that the liver has the first opportunity to process absorbed nutrients and detoxify blood before it enters the systemic circulation.
In summary, the hepatic portal system is a vital part of the circulatory system that links the digestive tract to the liver.
10. Give an account of blood pressure in man.
Answer: Blood pressure is the force exerted by circulating blood against the walls of blood vessels. It is essential for driving blood through the circulatory system.
Measurement:
Measured in millimeters of mercury (mmHg) using a sphygmomanometer. Expressed as systolic/diastolic (e.g., 12080 mmHg). Systolic Pressure: Pressure during ventricular contraction (highest). Diastolic Pressure: Pressure during ventricular relaxation (lowest).
Regulation:
Cardiac Output: Determined by heart rate and stroke volume. Peripheral Resistance: Determined by blood vessel diameter and blood viscosity. Blood Volume: Regulated by kidneys and hormones. Hormones: Epinephrine, norepinephrine, angiotensin II, aldosterone, and ADH. Nervous System: Sympathetic and parasympathetic nerves.
Factors Affecting Blood Pressure:
Age, gender, exercise, stress, diet, and disease.
Abnormalities:
Hypertension: High blood pressure (>14090 mmHg). Increases risk of heart attack, stroke, and kidney disease. Hypotension: Low blood pressure (<9060 mmHg). Can cause dizziness and fainting.
In summary, blood pressure is a vital sign reflecting cardiovascular health. It is tightly regulated by multiple physiological mechanisms.
11. Compare the rate of blood flow through arteries, arterioles, capillaries, venules and veins.
Answer: The rate of blood flow varies in different types of blood vessels due to differences in their structure and total cross-sectional area.
1. Aorta and Large Arteries:
Flow Rate: Fastest (about 30-40 cm/s). Reason: Small total cross-sectional area, high pressure from ventricular contraction.
2. Arterioles:
Flow Rate: Slower. Reason: Smaller diameter, but total cross-sectional area is larger than arteries. They are major resistance vessels.
3. Capillaries:
Flow Rate: Slowest (about 0.03 cm/s). Reason: Huge total cross-sectional area (largest of all vessels). This slow flow allows time for exchange of gases, nutrients, and waste.
4. Venules:
Flow Rate: Increases again. Reason: Total cross-sectional area decreases as venules merge into veins.
5. Veins and Vena Cava:
Flow Rate: Faster than capillaries, but slower than arteries (about 15 cm/s). Reason: Large diameter, low resistance, but low pressure.
Summary: Flow velocity is inversely proportional to total cross-sectional area. It is highest in the aorta and lowest in the capillaries.
In summary, the rate of blood flow is adapted to the function of each vessel type, ensuring efficient transport and exchange.
12. Explain the following:
a. Principle of angiography
Answer: Angiography is a medical imaging technique used to visualize the inside of blood vessels. A contrast dye is injected into the bloodstream, and X-rays are taken. The dye makes the blood vessels visible on the X-ray images. It is used to detect blockages,
aneurysms, and other vascular abnormalities. It can be used for diagnosis and for guiding interventions like angioplasty.
b. Coronary bypass
Answer: Coronary bypass surgery is a procedure to restore blood flow to the heart muscle. A healthy blood vessel (graft) is taken from another part of the body (e.g., leg, arm, chest) and connected to the coronary artery above and below the blocked area. This creates a new pathway for blood to flow around the blockage. It relieves angina and reduces the risk of heart attack.
c. Angioplasty
Answer: Angioplasty is a minimally invasive procedure to open narrowed or blocked blood vessels. A balloon catheter is inserted into the vessel and inflated to compress the plaque against the vessel wall. A stent (mesh tube) is often placed to keep the vessel open. It improves blood flow and relieves symptoms.
d. Open heart surgery
Answer: Open heart surgery is a major surgical procedure where the chest is opened and the heart is exposed. It is used to repair heart defects, replace valves, perform coronary bypass, or transplant the heart. The patient is often connected to a heart-lung machine to circulate blood during the surgery. It is a complex procedure with significant risks.
13. Explain hypertension and hypotension. What are the factors that regulate blood pressure?
Answer: Hypertension (High Blood Pressure): A condition where blood pressure is persistently elevated above 14090 mmHg. It is a major risk factor for heart attack, stroke, kidney disease, and vision loss. It is often asymptomatic (the "silent killer"). Causes include genetics, high salt intake, obesity, stress, and smoking.
Hypotension (Low Blood Pressure): A condition where blood pressure is abnormally low, usually below 9060 mmHg. It can cause dizziness, fainting, and fatigue. Causes include dehydration, blood loss, medication, and endocrine disorders.
Factors Regulating Blood Pressure:
Cardiac Output: Heart rate and stroke volume.
Peripheral Resistance: Blood vessel diameter and blood viscosity. Blood Volume: Regulated by kidneys and hormones (aldosterone, ADH). Hormones: Epinephrine, norepinephrine, angiotensin II, and ANP. Nervous System: Sympathetic and parasympathetic nerves. Baroreceptors: Detect changes in pressure and send signals to the brain.
In summary, blood pressure is tightly regulated by multiple mechanisms. Imbalances lead to hypertension or hypotension, both of which have serious health consequences.
14. Describe the lymphatic system of man.
Answer: The lymphatic system is a network of tissues, vessels, and organs that work together to maintain fluid balance, absorb fats, and defend against pathogens.
Components:
Lymph: A clear fluid similar to plasma but with less protein. It contains lymphocytes and waste products. Lymphatic Vessels: A network of thin-walled vessels that collect lymph from tissues. They have valves to prevent backflow. Lymph moves through them via skeletal muscle contractions and breathing. Lymph Nodes: Small, bean-shaped structures located along lymphatic vessels. They filter lymph and contain lymphocytes and macrophages that fight infection. Lymphatic Organs:
Spleen: Filters blood, stores lymphocytes, and destroys old red blood cells. Thymus: Matures T lymphocytes. Tonsils: Protect against pathogens entering the throat. Bone Marrow: Produces lymphocytes.
Functions:
Fluid Balance: Returns excess interstitial fluid to the blood. Fat Absorption: Absorbs fats and fat-soluble vitamins from the small intestine via lacteals. Immunity: Filters pathogens, produces lymphocytes, and initiates immune responses.
Clinical Significance: Blockage of lymphatic vessels causes edema (swelling). Lymph node swelling indicates infection or cancer.
In summary, the lymphatic system is essential for fluid homeostasis, lipid absorption, and immune defense.
