Bio Unit 5-6 Notes PDF

# The Respiratory System ## Introduction The respiratory system is designed to maximize gas exchange across the tissues of the body. It encompasses two main processes, and there are many structures involved that span other body systems, as well. The goal is to deliver oxygen to the body's tissues a...

# The Respiratory System ## Introduction The respiratory system is designed to maximize gas exchange across the tissues of the body. It encompasses two main processes, and there are many structures involved that span other body systems, as well. The goal is to deliver oxygen to the body's tissues and remove carbon dioxide. You will need to understand the order of organs air passes, specializations the organs have, as well as what happens to gases once they diffuse into the body, as there are several pathways these gases can take. ## The Respiratory System: A Diagram - **Sinus:** Open cavities in the skull that are lined by mucous membranes, which moisten and warm air. - **Nasal Cavity:** The nose is lined with mucous membranes that humidify and filter incoming air. Cilia hairs also clean and trap debris before exiting the nose. - **Oral Cavity:** The mouth can also be used to breathe during exercise. - **Adenoid:** A lymphatic tissue in the back of the nasal cavity. - **Tonsil:** A lymphatic tissue in the back of the oral cavity. - **Pharynx:** Shared space at the back of the throat between the nasal cavity and mouth. It is a common passage for air and food. - **Epiglottis:** A flap of tissue that covers the opening to the trachea to prevent food from entering the airway. - **Larynx:** The voice box, where vocal cords sit and produce sound. - **Trachea:** Also known as the windpipe, it is lined with Cilia hairs that beat rhythmically to move debris-laden mucus up the trachea and out. Once it hits the pharynx, it is either coughed out of swallowed. - **Esophagus:** Connects the pharynx to the stomach. - **Right Bronchus:** One of two tubes that branch off the trachea, leading to the right lung. - **Right Lung:** One of two organs responsible for gas exchange. - **Diaphragm:** A muscular band that separates the thoracic cavity from the abdominal cavity. When it contracts, it pulls the lungs downward, forcing air into them (inhalation). The opposite occurs when it relaxes. - **Bronchiole:** Small branches of the Bronchi. They are numerous and contain no cartilage for support. - **Alveoli:** Means "little cavity." These are the ends of the bronchioles and are shaped like little balloons. We think of these as the "inside" of the lungs, but they make up the lungs themselves. They are made of simple squamous epithelium and are covered in a thin film of moisture. - **Pulmonary Artery:** Carries deoxygenated blood to the lungs. - **Pulmonary Vein:** Carries oxygenated blood to the heart. - **Capillaries:** Connect arteries and veins. They are very small and thin, which allows for gas exchange between the blood and the tissues. - **RIBS:** The bony structure that protects the lungs. - **Pleura:** A membrane that surrounds the lungs. The inter-pleural space is filled with fluid, creating a vacuum which helps keep the lungs open. - **Pleural Space:** The space between the two layers of pleura. It is filled with a lubricating fluid which allows the two layers of pleura to slide over one another. - **Cilia:** Microscopic hairs that move mucus and trapped debris. - **Cells:** The smallest unit of life. - **Mucus:** Sticky substance that traps dirt and pathogens. ## Structures - **Nasal Cavity:** This space is where breathed in air is warmed, filtered, and moistened. - The nose and nasal cavity are lined with mucous membranes, a type of epithelial tissue that produces mucus. Mucous helps humidify the incoming air, while also trapping debris. - The nose also contains cilia thairs that clean and trap debris in the air before pushing it out of the nose. - **Pharynx:** The pharynx is the shared space at the back of the throat between the nasal cavity and mouth. It is the common passage for air and food. - **Glottis:** The end of the pharynx and start of the upper windpipe. - It is covered by the epiglottis when swallowing. This way, you can never breathe at the same time - otherwise, you'd choke! - **Larynx:** The space right under the glottis, leading into the windpipe. It is also called the "voice box" and contains the vocal cords. - Vocal cords are two bands of muscle that open or close depending on if you're breathing or speaking. When speaking, they are closed and will vibrate together as air passes them. The frequency of the vibrations, as well as the movement of other structures (tongue, lips, teeth, palate) produces different pitches in your speaking voice. - The vocal cords are protected on the outside by a cartilaginous structure called the "Adam's Apple." - **Trachea:** Also known overall as the windpipe. - It is composed of multiple rings of cartilage to prevent it from collapsing. The tube leads all the way down to the lungs. - It is lined with cilia, which beat rhythmically to move debris-laden mucus the up trachea and out. Once it hits the pharynx, it is either coughed out or swallowed. - **Bronchi:** These are branches of the trachea. One goes to each lung. They are still rigid with cartilage. - **Bronchioles:** Smaller branches of the bronchi. They are numerous and contain no cartilage for support. - **Alveoli:**Means "little cavity" these are the ends of the bronchioles and are shaped like little balloons. We think of these as the "inside" of the lungs, but they make up the lungs themselves. - They are made of simple squamous epithelium. Why must they be so thin? - Diffusion can happen more quickly (less distance!) ## What Happens to Air on its way to the Aveoli? 1. **Cleaned of debris:** - Initial cleaning occurs by the nose hairs and mucous in the nasal cavity. - The mucous membranes and cilia line the entire tract along the trachea and bronchi. - Mucous traps debris and cilia beat it upwards until it is swallowed or coughed out. 2. **Adjusted to body temperature:** - The more contact that occurs between air and moist tissues, the closer the acclimates to tissue temperature (about 37 degrees celsius). - When it reaches the alveoli, there is no difference in temperature between the air and the alveoli. 3. **Adjusted to 100% humidity:** - The air becomes saturated with water as it passes moist mucous pathways. - The lungs are also saturated with water (a product of repiration). ## Specializations of the Alveoli - Alveoli are numerous: there are up to 300 million in a single human lung! Why so many? SURFACE AREA!!! - Only one cell layer thick. - Each alveolus has a coating of lipoprotein on its inner surface. This helps maintain surface tension to prevent the alveoli from collapsing and sticking together. - Stretch receptors signal when the alveoli are full of air so the body can exhale. - They are highly vascularized, meaning there are capillary networks surrounding each alveolus. ## Some Extra Structures that Aid in Breathing... 1. **Pleural Membranes** - Create the surfaces of the lungs. - There are two sets of pleural membranes that make up the lungs. - 1 membrane is directly joined to the lung (contains the alveoli) - 1 membrane is joined to the ribs + diaphragm on the outside of the first membrane. - Both are separated by a fluid creating a vacuum. This is referred to as the intrapleural space. - The pressure in the intrapleural space is maintained at a level that is lower than atmospheric pressure. This holds the lungs open. - If any part of the membrane punctures, air will enter the intrapleural space, and the lungs will collapse. - The pleural membranes also allow the surfaces of the lungs to slide over the inner body wall easily (reducing friction). And seals off the thoracic cavity. 2. **Thoracic Cavity:** Also known as the chest cavity - it encompasses the area from the larynx to the diaphragm. 3. **Diaphragm:** This is a horizontal band of muscle just below the lungs. It is attached to the outer pleural membrane. - It separates the thoracic cavity from the abdominal cavity (the digestive system and its accessory organs). - When it contracts, it pulls the lungs downward, forcing air into them (inhalation). The opposite occurs when it relaxes. 4. **Ribs:** Help protect the internal organs and lungs. - Rib bones are surrounded by the intercostal muscles. When they contract, the thoracic cavity rises and increases in volume, thus forcing air into the lungs (inhalation). ## Unit 5: The Respiratory System The Respiratory System supplies the body with oxygen for energy production. Without oxygen, the body would shut down in minutes. The Respiratory System works closely with the circulatory system to allow oxygen to get to all the cells in the body, and for carbon dioxide to be removed. ### Four Processes: 1. **Breathing** (two processes) - **Inspiration:** Bringing air into the lungs. - **Expiration:** Expelling CO2 out of the lungs. 2. **External Respiration:** Exchange of gases between the lungs and the blood. 3. **Internal Respiration:** Exchange of gases between the blood and body tissues/Lells. 4. **Cellular Respiration:** Production of ATP within cells. FORMULA: $C_6H_{12}O_6 + O_2 → CO_2 + H_2O + ATP$ ## Breathing: Inhalation and Exhalation ### Inhalation: A step-by-step guide... 1. The concentrations of CO2 and H+ are the primary stimuli that cause us to breathe. 2. When [CO2] and [H+] are too high, the breathing center in the brain is stimulated. 3. A nerve impulse is sent from the Medulla Oblongata to the ribs and diaphragm which are attached to the lungs. 4. The diaphragm contracts and lowers while the intercostal muscles of the ribs contract to raise the ribs. 5. These actions increase the size of the chest cavity, thereby increasing it's volume. 6. At the same time, there is a decrease in air pressure due to a partial vacuum being creating in the lungs. 7. The air pressure in the lungs is reduced so much that air rushes in from outside to rebalance the pressure #### **NOTE:** Air enters because the lungs have already opened. The air does not force the lungs open. The dramatic decrease in air pressure "sucks" air into the lungs. This is why it is said that we breathe through negative pressure ### Exhalation: Another step-by-step guide... 1. When the lungs are full, stretch receptors in alveoli are stimulated. 2. These receptors notify the Medulla Oblongata and it stops sending impulses to the ribs and diaphragm. 3. The diaphragm and ribs muscles relax and return to resting state. 4. This decreases the size of the chest cavity, therefore decreasing volume, and increasing air pressure. 5. Now that the air pressure higher than the outside air pressure, air is forced out of the lungs. ## In addition to the Respiratory Center in the Medulla Oblongata, there are other receptors that can respond to stimuli: - Carotid bodies - in the carotid artery - Aortic bodies - in the aorta These respond to high concentration of Hydrogen ions (H+) but can also respond to levels of carbon dioxide in the blood. ## Gas Exchange: General Rules - When CO2 diffuses into the blood from the tissues, 9% is held in solution as dissolved CO2. - 27% attaches to hemoglobin to form carbaminohemoglobin (HbCO2). - The remaining 64% reacts with water to form bicarbonate ion (HCO3-) and Hydrogen ion (H+). $CO_2 + H_2O → HCO_3^- + H^+$ ## External Respiration: From the Lungs to the Blood - High concentrations of O2 in alveoli of the lungs cause the diffusion of O2 into blood stream along its concentration gradient. - In the blood stream, O2 joins with reduced hemoglobin (Hb) to form oxyhemoglobin (HbO2) and H+. - H+ ions are picked up by bicarbonate ion (HCO3^-) to temporarily form carbonic acid, which breaks down immediately to produce CO2 + H2O, which diffuses into the alveoli of the lungs to be exhaled. - Dissolved CO2 (9%) that is carried in the blood plasma diffuses into alveoli of the lungs to be exhaled. - Carbaminohemoglobin breaks down into CO2 and hemoglobin. CO2 diffuses into the lungs and is exhaled while hemoglobin picks up oxygen. ## This means that O2 attaches to hemoglobin in two contexts: - reduced hemoglobin and carbaminohemoglobin. - $O_2 + HHb → HbO_2 + H^+$ - $O_2 + HbCO_2 → HbO_2 + CO_2$ ## IMPORTANT NOTES: - H+ ions do not accumulate in the blood surrounding the lungs because as soon as it is released from hemoglobin, it combines with HCO3- to form carbonic acid, which breaks down right away (assisted by carbonic anhydrase) into CO2 and H2O. These diffuse into the lungs and are expelled. In this way, HCO3^- acts as a bufffer at the lungs to keep pH Stable! - Hemoglobin also acts like a buffer: it serves as a carrier for O2, CO2, and H+, so it acts like a buffer at the tissues of the body! ## Internal Respiration: Blood -> Tissues ### Remember... - 9% of CO2 diffuses from the tissues of the body into the blood stream and travels as dissolved CO2. - 27% of CO2 binds to hemoglobin to form carbaminohemoglobin. - 64% of CO2 reacts with water to temporarily form Carbonic Acid ($H_2CO_3$), which breaks down right away to bicarbonate ion ($HCO_3^-$) and H+ (facilitated by carbonic anhydrase). - CO2 will diffuse out of the tissues with its concentration gradient. 9% will remain dissolved in blood, 27% will bind to hemoglobin, and 64% will react with water in the blood. - Most of the released H+ from the carbon acid reaction reacts with oxyhemoglobin ($HbO_2$) at the tissues to form reduced hemoglobin ($HHb$). This causes the release of O2, which can diffuse with its concentration gradient into the tissues. The remaining hemoglobin that does not bind H+ will bind CO2 (27%). - The blood leaving the tissues now contain large quantities of carbaminohemoglobin and reduced hemoglobin. The blood also contains large amounts of HCO3-. No further changes occur until the blood reaches the lungs. ## **Be sure you understand all the equations shown in the diagrams above. Be able to name all the molecules and identify the equations as external respiration (It's easy if you just reverse the equations from one type of respiration).** - **External:** - $HHb + O_2 → HbO_2 + H^+$ - $Hb + CO_2 → HbCO_2$ - $HHb → Hb + H^+$ - $HCO_3^- + H+ → H_2CO_3 → CO_2 + H_2O$ - **Internal:** - $HbO_2 + CO_2 → HbCO_2 + O_2$ - $HbO_2 + H+ → HHb + O_2$ - $CO_2 + H_2O → H_2CO_3 → HCO_3^- + H^+$ # Unit 6: The Circulatory System ## Introduction The circulatory system is a complex network of vessels and organs that transport blood around the body. The goal is to deliver oxygen and nutrients to all cells, while removing carbon dioxide and wastes. It is also referred to as the cardiovascular system: Cardio refers to the heart, while vascular refers to the blood vessels. ## Let's Jump Right Into The Structures! 1. **Arteries:** - Structure: Made of thick, muscular, elastic tissues. They contain an inner layer of epithelium surrounded by a thick wall of smooth muscle. This is encased by connective tissue. The inner space has a small diameter. - Function: Arteries stretch when the ventricles eject blood from the heart, then push blood through. Large arteries branch to form arterioles. All arteries transport blood away from the heart. - Location: Found deep along the bones. 2. **Veins:** - Structure: Contain thin walls. They contain an inner layer of epithelium surrounded by a thin wall of smooth muscle (also encased by connective tissue). The inner space has a large diameter. Veins are unique in that they also contain valves, which allow blood to only flow in one direction. - Function: They will stretch slightly to accommodate incoming blood, then recoil to push it forward. The valves prevent blood from flowing backwards, as the veins do not recoil strongly enough to push blood against gravity. All veins transport blood back to the heart. - Location: Near the surface, surrounded by skeletal muscle. 3. **Capillaries:** - Structure: Are only one cell layer thick. They are made of simple squamous epithelium and are surrounded by sphincter muscles that dilate or constrict to control the flow of blood into the capillary bed. - If all capillaries dilate at once, blood pressure decreases. - If all capillaries constrict at once, blood pressure increases. - Function: Connect arteries to veins and provide the location for gas exchange between the blood and the tissues. - Location: Everywhere! All capillaries are within a few cells of each other, so all cells in the body can be "fed" by a capillary. 4. **Arterioles and Venules:** - Smaller scale versions of each vessel. Arterioles = smaller arteries; Venules = smaller veins. - Arterioles have sphincter muscles which can dilate or constrict to regulate blood pressure or change flow to a particular capillary bed. Arteries narrow into arterioles before entering capillary beds, while venules turn into veins the further blood travels away from capillary beds. - Some important terms: - Afferent = incoming; Efferent = outgoing. ### **Major Blood Vessels:** - A major blood vessel is a vessel that moves large volumes of blood towards or away from the heart. Damage to a major vessel would result in excessive blood loss and death. All major blood vessels narrow into normal (minor) vessels, which in turn narrow into capillary networks. 1. **Aorta:** - This major vessel leaves the left ventricle of the heart and loops over the heart in a curve called the aortic arch, which descends along the spine. - Structure: It is the largest artery in the body! It is similar in diameter to a garden hose. - Function: Transports blood away from the heart to the rest of the body. 2. **Coronary Arteries + Veins:** - Structure: These are the first branches of the aorta (arteries) and lie on the surface and inner parts of the heart. - Function: Feed the heart muscle. The veins take "spent blood" back to the heart to be reoxygenated. **Heart Attack:** blockage in coronary artery. 3. **Carotid Arteries:** - Structure: Two arteries that branch off the aortic arch and take blood to the head and brain. - Function: Highly specialized in detecting oxygen levels (chemoreceptors) and blood pressure (baroreceptors), as they contain nervous tissue. 4. **Jugular Veins:** - Structure: The counterparts to the carotid arteries. These do not contain valves, as they flow via gravity only to return to the heart. - Function: Conduct blood out of head to the Superior vena cava. 5. **Subclavian Arteries + Veins:** - Structure: Branch off the aortic arch and travel under the clavicle (collarbone). - Function: Conduct blood to and from the arms to drain back into the Superior vena cava. Drain products of lipid digestion. 6. **Renal Arteries + Veins:** - Structure: Branch off the dorsal aorta as it passes the lumbar region, descending. - Function: Take blood to and from the kidneys for filtering and back to the Posterior vena cava (inferior). 7. **Iliac Arteries + Veins:** - Structure: Branch off the dorsal aorta in the pelvic region. From there, it branches off into two arteries - one for each leg. The left and right common iliac veins come together in the abdomen to form the Posterior vena cava. - Function: Take blood to and from the legs and empty into the Posterior vena cava. 8. **Anterior/Superior and Posterior/Interior Vena Cava:** - Structure: These are the largest veins in the body. They are one vein that branches off into two directions. The Anterior Vena Cava brings blood back from the head, while the Posterior brings blood back from the rest of the body. - Function: Collects "spent blood" from all veins in the body and empties in to the right atrium of the heart. ## Unit 6: The Circulatory System: The Pulmonary and Systemic Circuits The circulatory system is composed of two circuits, that work closely together to deliver oxygen and transport waste around the body. These are called the Pulmonary Circuit and the Systemic Circuit. The difference between them lies in where blood is travelling, and what it is carrying. Pay close attention to whether the blood is oxygenated or deoxygenated. ### Pulmonary Circuit: - The Pulmonary Circuit is comprised of the right atrium + ventricle and pulmonary trunk, as well as arteries that deal strictly with the heart and the lungs. - The Pulmonary arteries, are the only arteries in the body that carry deoxygenated blood, while the pulmonary veins, are the only veins in the body that carry oxygenated blood. - Remember, the general function of the arteries is to carry blood away from the heart (efferent), and the function of veins is to carry blood to the heart (afferent). - The function of the pulmonary arteries is to bring deoxygenated blood from the right side of the heart (right ventricle) to the lungs to pick up oxygen for eventual transport to the whole body, while the pulmonary veins return oxygenated blood from the lungs to the left atrium of the heart, before pumping it all over the body. ### KEY SUMMARY: - Pulmonary Arteries bring deoxygenated blood from the right side of the heart to the lungs to pick up oxygen; pulmonary veins bring oxygenated blood from lungs to the left side of the heart. - **Right Ventricle -> Pulmonary Trunk -> Pulmonary Arteries -> Lung Capilaries-> Pulmonary Veins -> Left Atrium** ### Systemic Circuit: - The Systemic Circuit comprises the left atrium + ventricle of the heart, as well as the aorta. - It receives oxygenated blood from the lungs and pumps it to the entire body. - It's also responsible for receiving deoxygenated blood from the tissues and returning it to the heart, where it is oxygenated again, completing the cycle. - **Pulmonary Veins -> Left Atrium -> Left Ventricle -> Aorta -> Arteries that branch off the aorta (the large arteries that feed the rest of the body) -> Capillaries -> Veins that return the deoxygenated blood from capillaries to the Left Atrium.** ### Therefore, the heart is divided in half: - **The right half makes up the pulmonary circuit and contains deoxygenated blood, while the left half makes up the systemic circuit and contains oxygenated blood.** ### Blood Flow: Left Ventricle -> Aorta -> Arteries -> Capillaries -> Veins -> Vena Cava -> Right Atrium ## Cross Sectional Area There are several relationships governing the efficiency of blood vessels. These include: 1. **Blood vessel diameter:** Diameter refers to the size of the space inside a blood vessel. Generally, diameter is largest in the veins, similarly large in the arteries, and very small in the capillaries. Diameter has a great effect on blood pressure. - Arteries are surrounded by muscular walls that can dilate (vasodilate) or constrict (vasoconstrict) to adjust vessel diameter. Because diameter closely affects blood pressure, dilating blood vessels decreases blood pressure by allowing blood to flow through with less restriction. Constricting blood vessels causes more resistance, thus increasing blood pressure. 2. **Blood Velocity:** Blood velocity refers to how quickly blood travels through a vessel. Velocity is highest in the arteries and slows down drastically in the capillaries. This allows for more efficient gas exchange in the capillary networks. Blood velocity remains low in the veins, but it is faster than capillaries. Blood velocity is inversely proportional to total cross-sectional area. - As cross-sectional area increases, velocity of the blood decreases. Velocity decreases from arteries to arterioles to capillaries and increases slightly in venules and veins. 3. **Blood Pressure:** Blood Pressure is highest in the arteries and lowest in the capillaries. Once blood pressure is "lost" in the capillaries, it does not increase again when blood moves into the veins. The veins are too far from the heart, and veins do not contain muscles for vasoconstriction or vasodilation. 4. **Total Cross-Sectional Area:** Total cross-sectional area refers to the sum of the area of all blood vessels of a specific type in the circulatory system. Essentially, the more numerous the vessel type, the more total cross-sectional area there is. Capillaries have the highest cross-sectional area, while veins are second, and arteries are third. Despite arteries being large, they are less numerous and have a smaller overall diameter. #### **As the total cross-sectional area increases, vessel diameter and blood velocity decrease.** ## Can you answer these 3 questions without checking your notes? 1. **Which type of blood vessel has the highest blood pressure? Lowest?** *Artery; Veins + capillaries* 2. **Which type of blood vessel has the highest velocity? Lowest?** *Artery; Capillaries* 3. **Which type of blood vessel has the highest cross-sectional area? Lowest?** *Capillaries; Artery* 4. **Which type of blood vessel has the highest blood pressure? Lowest?** *Veins, Capillaries* ## Unit 6: The Circulatory System: What is Blood? Blood is a specialized body fluid in the circulatory systems of humans and other vertebrates whose purpose is to deliver oxygen and nutrients to cells, while transporting carbon dioxide and metabolic wastes away from cells. While blood is mostly water, it contains many other dissolved substances, cells, and proteins necessary for transporting things efficiently. ## Components of Blood Blood can be divided into two main categories: the plasma and the formed elements. Each is composed of different materials: 1. **Plasma:** Makes up 55% of total blood volume. - **Water (90%)** - **Plasma proteins + hormones** - **Dissolved gases (CO2 + O2)** - **Nutrients (monomers like glucose)** - **Salts** - **Wastes** - **Plasma:** - Water, proteins, nutrients, hormones, etc. 2. **Formed Elements:** Make up 45% of total blood volume. - **Buffy coat:** - White blood cells, platelets - **Hematocrit:** - Red blood cells ## Types of Blood Cells There are three main types of blood cells in the circulatory system. Each one has different physical attributes which make them well adapted to their respective purposes. We will explore all three types in detail here. 1. **Erythrocytes (also known as red blood cells)** - A red blood cell typically lives for about 120 days. - They are produced in the red bone marrow, which is a spongey tissue found in the center of many bones, such as the skull, ribs, vertebrae, and most long bones, leg and arms. - Red bone marrow produces stem cells, some of which will form the red blood cells. These stem cells are called erythroblasts. Erythroblasts will differentiate into erythrocyte before leaving the bone marrow and entering the blood stream. - About 5 million are produced every second! - All red blood cells are biconcave in shape and do not have a nucleus. - They contain a protein called hemoglobin, which contains iron. - Hemoglobin picks up oxygen in the lungs and releases it in tissues. It also has an affinity for carbon dioxide and H+ in tissues and releases it at the lungs. - In one red blood cell, there are approximately 200,000,000 hemoglobin molecules. - Anemia = lack of iron. - Red blood cells allow the blood to remain liquid, so the heart does not have to work as hard. If hemoglobin floated freely in the blood, it would be too thick, and the heart would have to pump harder to get oxygen around the body (increases blood pressure). - At the end of their lifespans, erythrocytes are destroyed in the liver and spleen. 2. **Leukocytes (also known as white blood cells)** - White blood cells are larger than red blood cells. They also stem from stem cells in the bone marrow (B cells) and can also originate in the thymus gland, in the lymphatic system (T cells). - These cells have nuclei, but no definite shape. - White blood cells are less numerous than red blood cells and are outnumbered 700:1! - Their main function is to fight against infection. Therefore, they are immune system cells. - There are several types of white blood cells: - **Neutrophils:** Kill bacteria, fungi, and foreign debris. - **Lymphocytes:** Protect against viral infections and produce antibodies. Most are found in the lymphatic system. - **Eosinophils:** Identify and destroy parasites and cancer cells. They also help your allergic response. - **Basophils:** Produce an allergic response. - **Monocytes:** Clean up damaged cells to prevent infection. - Many leukocytes are phagocytic, meaning they "eat" invaders and digest them in the cytoplasm using lysosomes. - Many produce antibodies, which help alert other white blood cells of an infection. 3. **Thrombocytes (also known as platelets)** - Platelets are produced from stem cells in the bone marrow. They are very small and are composed of broken fragments of larger cells. You produce about 2 billion a day! - Thrombocytes play an important role in blood clotting - without them, you would not be able to stop bleeding, and you would lose too much blood. - Platelets will clump at the site of the bleed and partially close it. Then the platelets and the injured tissue release an enzyme to further the clotting process. - In addition to platelets, there are many other chemical compounds necessary to initiate blood clotting. If even one is missing, it would have dire consequences. - Hemophilia = inability to clot blood ## Blood Clotting Cascade - When a blood vessel is damaged (i.e. by a cut), platelets flowing in the bloodstream begin clumping at the damaged area. This partially closes the "leak." - Platelets and damaged cells release a substance called Thromboplastin. - Now in the bloodstream, Thromboplastin converts a blood protein called Prothrombin, which is produced by the liver. Prothrombin is an activator protein and contains Potassium (K+). - Prothrombin is converted into a new, active substance called Thrombin (by Thromboplastin). - Thrombin is an enzyme that converts another blood protein called fibrinogen (also made by the liver) into an active protein called fibrin (clot). - Fibrin is sticky and forms a mesh-like network over the leak. Blood cells and more platelets get trapped and form the clot, which stops the flow of blood out of the vessel. Now the vessel can begin repairs. - The Fibrin clot is only temporarily present; as soon as the blood vessel repair is initiated, a new enzyme called plasmin destroys the network (fibrinolysis). ## Blood Types Blood types refer to the category of antibodies carried in the blood plasma, as well as the antigen proteins on the outside of blood cells. Antigens are the identifiers on cells that antibodies bind to. Once an antibody binds to an antigen, an immune response is triggered. Antibodies help flag pathogens as foreign so immune cells can dispose of them. There are four main blood types: A, B, AB, and O. Each type is n