Complete Notes on Blood Vessels, Heart, and Respiration

Blood Vessels

Objectives

• Compare the structure and function of blood vessels.

• Identify the materials transported between cells and capillaries.

Blood Vessels: Pathways of Circulation

Blood, being a fluid, flows through blood vessels. There are three main types:

1. Arteries

2. Veins

3. Capillaries

Arteries

• Large, thick-walled, muscular, and elastic blood vessels designed to withstand high pressure.

• Carry oxygenated blood away from the heart to various parts of the body (except for the pulmonary artery, which carries deoxygenated blood to the lungs).

• Blood is under great pressure due to the pumping action of the heart.

Blood Movement Through Arteries

• Heart contraction (systole) pushes blood through arteries, expanding the artery walls to accommodate the increased volume.

• Heart relaxation (diastole) causes the artery to shrink back, aiding in the propulsion of blood forward.

• Blood surges through arteries in pulses, with the pulsating rhythm corresponding to the heartbeat.

Branching Arteries

• Arteries divide into smaller arteries, which further branch into arterioles.

• Arterioles enter tissues and branch extensively into capillaries, ensuring every cell is within proximity for nutrient and waste exchange.

Capillaries

• Microscopic blood vessels with walls only one cell thick to facilitate efficient diffusion.

• Red blood cells move through them in single file, maximizing contact with the capillary walls.

• Form dense networks reaching almost every cell in the body, ensuring no cell is far from a capillary.

Universal Donors vs. Recipients

• Type O- is the universal donor because it lacks A, B, and Rh antigens on the RBC surface, minimizing the risk of immune reactions.

• Type AB+ is the universal recipient because it lacks anti-A, anti-B, and anti-Rh agglutinins (antibodies) in its plasma, allowing it to receive blood from any ABO and Rh blood type.

Diffusion between Tissues and Blood Cells

Diffusion

Capillary walls are thin, made up of a single layer of endothelial cells, enhancing the diffusion of gases, nutrients, and wastes between blood and tissue cells.

Materials Transported

Five types of materials are transported between cells and capillaries:

1. Carbon dioxide: Waste product from cellular respiration, transported from tissues to the lungs for exhalation.

2. Oxygen: Essential for cellular respiration, transported from the lungs to the tissues.

3. Hormones: Chemical messengers secreted by endocrine glands, transported via the bloodstream to target cells to regulate various physiological processes.

4. Nutrients: Include glucose, amino acids, fatty acids, vitamins, and minerals, transported from the digestive system to cells for energy and growth.

5. Nitrogenous wastes: Waste products such as urea and creatinine, transported from cells to the kidneys for excretion.

Veins

• Capillaries converge into venules as blood leaves tissues, starting the return journey to the heart.

• Venules merge to form veins, which carry blood back to the heart. Veins have thinner walls and larger lumens compared to arteries.

• Blood pressure in veins is significantly lower than in arteries; veins rely on other mechanisms to facilitate blood return to the heart.

Valves

• Some veins (especially in arms and legs) have valves to prevent backflow against gravity, ensuring unidirectional blood flow towards the heart.

• Skeletal muscle contraction squeezes the veins, forcing valves open and moving blood towards the heart. This is particularly important in the legs.

• Muscle relaxation causes valves to close, preventing backflow and ensuring blood continues to move in the correct direction.

Muscle Layers: Veins vs. Arteries

Cross-section comparison of vein and artery structures, highlighting differences in elastic and muscular fibres, collagen fibres, and lumen size. Arteries have thicker muscular and elastic layers to handle high pressure, while veins have thinner layers and larger lumens.

The Heart and the Cardiac Cycle

Objectives

• Discuss the purpose of the heart as the central pump ensuring blood circulates throughout the body.

• Describe the two pathways that blood takes: pulmonary and systemic circuits.

• Label the external and internal anatomy of the heart, including atria, ventricles, and valves.

• Describe the pathway of blood through the heart and whether or not blood is oxygenated.

Facts about the Heart

• The average human heart beats over $2.5 \text{ billion}$ times in 70 years, demonstrating its incredible endurance.

• The system of blood vessels (arteries, veins, and capillaries) is over $96000 \text{ km}$ long, showcasing the extensive network that ensures every cell receives nutrients and oxygen.

• An adult's heart is about the size of two clenched fists, located in the thoracic cavity, protected by the rib cage.

Heart Function

• The heart is the pump that drives the cardiovascular system, ensuring continuous blood circulation.

• Drives blood through the body, delivering oxygen, nutrients, hormones, and immune cells to tissues and organs.

• Blood flow is in a figure-eight pattern through the dual circuits: pulmonary and systemic.

Pathways of Blood

The heart pumps blood along two pathways:

1. Pulmonary circuit: Transports blood between the heart and the lungs for gas exchange.

2. Systemic circuit: Carries blood from the heart to the rest of the body and back.

The Pulmonary Circuit

• The heart pumps blood to the lungs and back; this circuit oxygenates the blood and removes carbon dioxide.

• Deoxygenated blood leaves the heart via the pulmonary artery, goes to the lungs, and oxygenated blood returns to the heart via the pulmonary vein.

$\text{Deoxygenated Blood} \rightarrow \text{Pulmonary Artery} \rightarrow \text{Lungs} \rightarrow \text{Pulmonary Vein} \rightarrow \text{Heart}$

The Systemic Circuit

• The systemic circuit carries blood from the heart to the body and back, delivering oxygen and nutrients to all tissues and removing waste products.

Oxygenated blood leaves the heart flows through body systems, deoxygenated blood enters via superior/inferior vena cava back to heart.

$\text{Oxygenated Blood} \rightarrow \text{Aorta} \rightarrow \text{Body Systems} \rightarrow \text{Superior/Inferior Vena Cava} \rightarrow \text{Heart}$

The Heart

• The heart consists of four chambers: right atrium, left atrium, right ventricle, left ventricle.

• It is a two-pump system; the right side handles deoxygenated blood, and the left side handles oxygenated blood.

• The right side pumps blood to the lungs, and the left side pumps blood to the rest of the body, working in coordination to maintain efficient circulation.

• The septum separates the two sides, preventing mixing of oxygen-rich and oxygen-poor blood, which is crucial for efficient oxygen delivery.

The 4 Chambers of the Heart

Atria

• Left and right atria receive blood returning to the heart from the pulmonary and systemic circuits, respectively.

• Blood is then transferred to the ventricles, priming them for the next phase of the cardiac cycle.

Ventricles

• Lower chambers of the heart, with thicker muscular walls compared to the atria, enabling them to pump blood to the lungs and the rest of the body.

• Right and left ventricles receive blood from the atria and pump it to the lungs and the rest of the body.

Valves in the Heart

Atrioventricular Valves

Separate the atrium from the ventricle, preventing backflow of blood during ventricular contraction.

• Tricuspid valve: Located between the right atrium and right ventricle, with three leaflets.

• Bicuspid (mitral) valve: Located between the left atrium and left ventricle, with two leaflets.

Semilunar Valves

Control blood flow leaving the ventricles, ensuring unidirectional flow into the pulmonary artery and the aorta.

• Pulmonary valve: Located at the entrance of the pulmonary artery, preventing backflow into the right ventricle.

• Aortic valve: Located at the entrance of the aorta, preventing backflow into the left ventricle.

Systole

• Contractions of the heart, during which blood is ejected into the pulmonary artery and the aorta.

• A 0.1-second contraction of the atria completely fills the ventricles with blood, maximizing preload.

• Followed by a 0.3-second contraction of the ventricles, generating high pressure to pump blood.

• This closes the atrioventricular valves and forces open the semilunar valves, ensuring blood flows out of the ventricles.

• Blood is pumped into the large arteries, ready to be distributed throughout the body.

• Blood also flows into the atria at this time, preparing for the next cardiac cycle.

Diastole

• During diastole, the entire heart is relaxed, allowing the chambers to fill with blood.

• The atrioventricular valves are open, facilitating the flow of blood from the atria to the ventricles.

• Blood flows into all four chambers, replenishing the volume in preparation for the next systole.

Lub-Dub

• Lub-Dub is the sound the heart makes with each heartbeat, resulting from the closing of the heart valves.

• Lub is heard when the tricuspid and mitral valves close at the start of ventricular systole.

• Dub is heard when the aortic and pulmonary valves close at the start of ventricular diastole.

• A heart murmur is heard when a valve cannot close all the way, resulting in turbulent blood flow and unusual heart sounds.

Electrical Control of the Heart & Blood Pressure

Objectives

• Describe how contractions of the heart are electrically controlled through specialized cardiac cells.

• Explain the various points on a PQRST electrocardiogram and what each represents in the cardiac cycle.

• Explain the difference between systolic and diastolic blood pressure readings and their clinical significance.

The Electrical System of the Heart

• Pumping of the heart is controlled by electrical impulses generated and conducted by specialized cardiac cells.

• An electrical impulse is generated by the sinoatrial (SA) node, also known as the pacemaker, located in the walls of the right atrium. The SA node initiates each heartbeat.

• The electrical impulse stimulates the muscles of the atria, causing them to contract and push blood into the ventricles.

• That electrical impulse reaches the atrioventricular (AV) node, which delays the impulse briefly before sending it to the ventricles.

• The AV node causes ventricles to contract, pumping blood to the lungs and the rest of the body.

Electrocardiograms (ECG)

• Electrical conduction of the heart can be monitored using an electrocardiogram (ECG), a non-invasive diagnostic tool.

• Abnormal patterns in conduction of impulses of the cardiac musculature can be monitored, helping to diagnose various heart conditions. These include flutters, arrhythmia, fibrillation, etc.\n- Electrocardiograms show a graphic representation of the heart rhythm, providing valuable insights into cardiac function.

• The parts of the graph are labeled P, QRS, and T, each representing a specific phase of the cardiac cycle.

ECG Components

• P wave: Represents the electrical activation (depolarization) of the atria, leading to atrial contraction.

• QRS complex: Represents the electrical activation (depolarization) of the ventricles, leading to ventricular contraction.

• T wave: Represents the recovery wave (repolarization) of the ventricles, as the ventricular muscle cells reset electrically.

*Atrial Depolarisation

*Ventricular Depolarisation

*Repolarization

*PR Interval: represents the time between atrial depolarization and ventricular depolarization.

*QT Interval: represents the time between ventricular depolarization and repolarization.

Blood Pressure

• Blood pressure is the force that the blood exerts on the blood vessels, crucial for maintaining adequate blood flow to all tissues.

• This pressure rises during heart ventricular contraction (systolic pressure) and lowers during ventricular relaxation (diastolic pressure), creating the pulsatile nature of blood flow.

• Blood pressure is highest in the arteries and decreases through smaller arterioles and capillaries, where nutrient and waste exchange occurs.

How Blood Pressure is Measured

• Blood pressure is measured with a sphygmomanometer, a device consisting of an inflatable cuff and a manometer.

• The blood pressure cuff inflates, and the column of mercury or a digital sensor indicates the pressure.

• Pressure is measured during the systole phase when the heart contracts and in the diastole phase when the heart relaxes.

• An average blood pressure reading in the brachial artery (upper arm) is $120/80$ mmHg, where 120 is systolic pressure and 80 is diastolic pressure.

Arterial Hypertension (High Blood Pressure)

• High blood pressure is characterized by having a systolic pressure consistently greater than 140 mmHg or a diastolic pressure greater than 90 mmHg.

Factors Contributing to Hypertension

1. Age: Blood pressure tends to increase with age due to stiffening of arteries.

2. Diet: High sodium intake and low potassium intake can elevate blood pressure.

3. Obesity: Excess body weight increases blood volume and cardiac output.

4. Drinking: Excessive alcohol consumption can raise blood pressure.

5. Lack of exercise: Sedentary lifestyle contributes to increased blood pressure.

6. Stress: Chronic stress can lead to elevated blood pressure levels.

• High arterial pressure increases the workload of the heart - the heart tends to thicken, enlarge, and weaken over time, leading to heart failure.

• Persistent hypertension is one of the risk factors for strokes, heart attacks, and chronic renal failure (kidney failure), emphasizing the importance of managing blood pressure.

Hypotension

• Hypotension is abnormally low blood pressure, which can result in inadequate blood flow to vital organs.

• A person has hypotension if their systolic pressure is less than 90 mmHg or if their diastolic pressure is less than 60 mmHg.

• It can be caused by low blood volume, hormonal changes, medicine, or anemia.

• Low blood pressure can cause dizziness and fainting due to insufficient blood flow to the brain.

• Severely low blood pressure can deprive the brain and other vital organs of oxygen and nutrients - this condition is called shock, which is life-threatening.

Homeostasis via the Transportation Systems

Objectives

Explain how transport systems help to maintain homeostasis in the body.

Include: transport nutrients, oxygen, carbon dioxide, wastes, and hormones; help maintain fluid balance; regulate body temperature; and assist in the defense of the body against invading organisms.

Hormone Transportation

Hormones are chemical messengers in the body that control most bodily functions. Hormones are secreted by endocrine glands and travel through the bloodstream to reach target cells.

Hormones have specific target cells that they interact with to cause a particular change or effect in those cells. This interaction involves hormone receptors on target cells.

Hormones use the circulatory system to travel to these target cells to make a change regulated by the brain. The brain monitors hormone levels and adjusts hormone secretion to maintain homeostasis.

EX. Estrogen-responsible for causing puberty, prepares uterus for pregnancy, and regulates menstrual cycle. This hormone is made in the ovaries and then is transported through the body by the circulatory system to female reproductive organs to start these processes.

Nutrient/Waste Transportation

As we know from the digestive system, all the food molecules are absorbed into the bloodstream. The small intestine is the primary site of nutrient absorption.

These molecules are required by every cell in the body to survive. Nutrients provide energy and building blocks for cellular processes.

Remember that plasma carries these nutrients in it to bring it to the cells. Plasma, the liquid component of blood, transports nutrients, hormones, and waste products.

The transportation system can reach every cell in the body which makes it capable of delivering food molecules so every cell can absorb them. Capillaries facilitate the exchange of nutrients and wastes between the blood and cells.

There are wastes involved with cell processes that the cell must get rid of. Metabolic wastes include carbon dioxide, urea, and other nitrogenous compounds.
The transportation system will send wastes to the excretory system organs (liver, kidneys). The liver processes and detoxifies many waste products, while the kidneys filter waste from the blood to produce urine.

Oxygen/Carbon Dioxide Transportation

Remember that every cell in the body requires oxygen to create energy (ATP). Oxygen is essential for cellular respiration in the mitochondria.

The transportation system and the respiration system are incredibly intertwined to allow for oxygen to be absorbed regularly into the blood stream to send to cells (via erythrocytes- red blood cells). Red blood cells contain hemoglobin, which binds to oxygen for efficient transport.

A byproduct of energy formation is carbon dioxide that the body is unable to use. Carbon dioxide is a waste product of cellular respiration.

The cells release CO2 back into the blood stream where the blood returns it to the lungs to be expelled during exhalation. Carbon dioxide is transported in the blood in three forms: dissolved in plasma, bound to hemoglobin, and as bicarbonate ions.

Temperature Regulation

Remember that the human body processes work best within a very narrow range. The body maintains a stable internal temperature (around $37^\circ C$) through thermoregulation.

If the body gets too warm, the blood vessels receive messages to dilate (grow bigger in diameter) especially near the surface of the skin. Vasodilation increases blood flow to the skin, allowing heat to dissipate.

The greater surface area of the blood vessels allow for extra heat to be release through radiation, convection, and evaporation.

If the body gets too cold, the blood vessels constrict to keep the heat in. Vasoconstriction reduces blood flow to the skin, conserving heat.

Respiration

Objectives

• Describe the function of the respiratory system and specify 3 types of respiration.

• Discuss the homeostatic role of the respiratory system.

• Describe the anatomical components of the respiratory system.

Functions of the Respiratory System

• The respiratory system works closely with the circulatory system to facilitate gas exchange.

• It takes oxygen from the air and supplies it to the blood for transport to tissue cells, supporting cellular respiration.

• It removes and disposes of carbon dioxide from blood, a waste product of cellular respiration.

Types of Respiration

Respiration includes all of the mechanisms that are used to get oxygen to the body cells.

There are 3 categories of respiration:

1. Cell Respiration

2. Internal Respiration

3. External Respiration

Cellular Respiration

• Cellular respiration occurs inside our cells in the mitochondria, where energy production takes place.

• The mitochondria use oxygen to break carbohydrates (glucose) into ATP (energy) and release carbon dioxide as waste.

$C<em>6H</em>{12}O<em>6 \rightarrow CO</em>2 + H_2O + ATP$.

Internal Respiration

• Internal respiration involves the exchange of oxygen or carbon dioxide between the body cells/tissue and their surrounding blood capillaries in the body, allowing oxygen delivery and carbon dioxide removal at the cellular level.

External Respiration

• External respiration involves the exchange of oxygen or carbon dioxide between the air in the lungs alveoli and the blood that circulates around the walls of the aveli, facilitating the uptake of oxygen and elimination of carbon dioxide from the body.

The Homeostatic Role of the Respiratory System

The respiratory system has 2 roles in maintaining homeostasis:

1. Gas Exchange - Oxygen in Carbon Dioxide out ensures the body has adequate oxygen and removes carbon dioxide waste effectively

2. Regulation of Blood PH - The respiratory system helps regulate blood pH by controlling the levels of carbon dioxide in the blood.

Anatomical Components of the Respiratory System

Air goes through the following structures:

• Nasal Cavity

• Pharynx (Throat)

• Larynx (Voice Box)

• Trachea (Windpipe)

• Bronchi

• Bronchioles

• Alveoli (Site of Gas Exchange)

The Nasal Cavity

• In the nasal cavity, air enters nostrils and is filtered by hair, warmed, and humidified as it flows through a maze of spaces, preparing the air for entry into the lower respiratory tract.

Pharynx

• The pharynx is the intersection where pathways for air and food cross, serving both the respiratory and digestive systems.

• Most of the time, the pathway for air is open, except when we swallow, during which the epiglottis closes to prevent food from entering the trachea.

• The epiglottis acts as a doorway, closing off the esophagus when we are breathing, and closing off the trachea when we are swallowing.

Larynx (Voice Box)

• The larynx is reinforced with cartilage, providing structure and support to the airway.

• It contains vocal cords which allow us to make sounds by voluntarily tensing muscles and controlling airflow, enabling speech and vocalization.

Trachea

• The trachea transports the oxygen from the pharynx to the bronchi, ensuring a clear pathway for air to enter the lungs.

• The trachea has rings of cartilage, providing support and preventing collapse during breathing.

• These prevent the trachea from closing, ensuring uninterrupted airflow to the lungs.

Bronchi

• Each bronchus leads into a lung, dividing into smaller airways to distribute air throughout the lung tissue.

• They branch into smaller and smaller bronchioles resembling an inverted tree, forming the bronchial tree.

Bronchioles

• Bronchioles are fine tubes that allow the passage of air, delivering air to the alveoli for gas exchange.

• The surface of the bronchioles is covered with cilia, which helps to clear mucus and debris from the airways.

• Mucus traps dust and other particles, preventing them from reaching the delicate alveoli.

• Cilia beat upwards and remove trapped particles and mucus from lower respiratory airways, keeping the airways clean and clear.

Alveoli

• Alveoli are the site of Gas changes with the circulatory system, where oxygen and carbon dioxide are exchanged between the air and the blood.

• The cell walls of alveoli are only 1 call thick, maximizing the diffusion of gases.

• Oxygen diffuses from the lungs into the blood stream, and Carbon dioxide diffuses from the blood stream into the lungs for exhalation, facilitating efficient gas exchange.

Breathing and Control of Breathing

Objectives

• Explain how muscles are involved in inhalation and exhalation, and how the diaphragm and intercostal muscles contribute to the process.

• Describe how breathing is regulated through negative feedback cycles, and how the brain monitors and adjusts breathing rate and depth.

Phases of Breathing

Breathing consists of 2 phases:

1. Inhalation

2. Exhalation

Inhalation (Inspiration)

• During inhalation, the diaphragm and intercostal muscles contract, increasing the volume of the thoracic cavity.

• This increases the volume of the thoracic (chest cavity) and draws air into the lungs, creating a pressure gradient that pulls air into the airways.

Exhalation (Expiration)

• During exhalation, the diaphragm and intercostal muscles relax, decreasing the volume of the thoracic cavity.

• This returns the thoracic cavity to its original volume, increasing pressure in the lungs and forcing air out.

Respiration is controlled by a part of the brain called the medulla oblongata, which is the primary control center for breathing.

Respiration is controlled by a negative feedback cycle, which helps the body maintain homeostasis by adjusting breathing rate and depth in response to changes in blood oxygen and carbon dioxide levels.

Control of Breathing

*Medulla oblongata in the Brain controls breathing by monitoring blood pH and CO2 levels.

*Blood PH and Concentration of CO2 are the main factors influencing breathing rate and depth.

Body uses oxygen faster and produce Carbon dioxide waste during exercise, leading to increased CO2 levels in the blood.

*Brain