Bio 6.1 Circulatory System PDF

# Unit 6: The circulatory System ## Introduction The circulatory system is a complex network of vessels and organs that transport blood all around the body. The goal is to deliver oxygen & nutrients to all cells, while removing Carbon dioxide + wastes. It is also referred to as the **cardiovascula...

# Unit 6: The circulatory System ## Introduction The circulatory system is a complex network of vessels and organs that transport blood all around the body. The goal is to deliver oxygen & nutrients to all cells, while removing Carbon dioxide + 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 recoil, which pushes 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 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 and 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 deoxygenated "spent blood" back to the heart to be oxygenated.\ - **Heart Attack:** blockage in coronary artery. ### 3. Carotid Arteries - **Structure:** Two arteries that branch off the aortic arch and take blood to the head & brain. - **Function:** Highly specialized in detecting oxygen levels (chemoreceptors) and blood pressure (haroreceptors), 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 Anterior/Superior/ Posterior/Interior vena cava. ### 8. Anterior/Superior/ 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 it into the right atrium of the heart.