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Ch 42 (Lymph circulation (((Lymph vessels have valves that prevent the…

- - - - Lymph vessels have valves that prevent the backflow of fluid
      - skeletal muscle contractions play a role in moving lymph
      - lymphatic system plays a role in harmful immune responses, such as those responsible for asthma
      - lymph nodes-play an important role in the body’s defense
      - movement of lymph from peripheral tissues to the heart relies on many of the same mechanisms that assist blood flow in veins
      - The recovered fluid, called lymph, circulates within the lymphatic system before draining into a pair of large veins of the cardiovascular system at the base of the neck
      - Fluid diffuses into the lymphatic system via a network of tiny vessels intermingled with capillaries
      - lost fluid and the proteins within it are recovered and returned to the blood via the lymphatic system
      - Each day the adult human body loses approximately 4–8 L of fluid from capillaries to the surrounding tissues
- - - - vasodilation- smooth muscles relax, the arterioles increase in diameter that causes blood pressure in the arteries to fall
      - vasoconstriction-smooth muscles in arteriole walls contract, the arterioles narrow
      - Measured from an artery in arm at the same height as heart.
      - Regulation of Blood Pressure
      - Gravity has a significant effect on blood pressure
      - Homeostatic mechanisms regulate arterial blood pressure by altering the diameter of arterioles
      - Diastolic pressure-the elastic walls of the arteries snap back. As a consequence, there is a lower but still substantial blood pressure when the ventricles are relaxed
      - Normal blood pressure 120/80
      - systolic pressure - Arterial blood pressure is highest when the heart contracts during ventricular systole
      - Heart- the site of highest pressure
      - Blood flows from areas of higher pressure to areas of lower pressure. Contraction of a heart ventricle generates blood pressure
- - - - What does a circulatory system do?
      - They link exchange surfaces with cells throughout the body
      - How they do it?
      - Small molecules in and around cells, including O2 and CO2, undergo diffusion, which is random thermal motion
      - The molecular trade that an animal carries out with its environment (gaining O2 and nutrients, and releasing CO2), must eventually involve every cell in the body.
      - simple body plan- places many or all cells in direct contact with the environment.
        Each cell can thus exchange materials directly with the surrounding medium
      - How does each cell of an animal participate in exchange?
      - A circulatory system-move fluid between each cell’s immediate surroundings and the body tissues. As a result, exchange with the environment and exchange with body tissues both occur over very short distances
      - A central Gastrovascular Cavities
      - In hydras, jellies, and other cnidarians
      - functions- in the distribution of substances throughout the body, as well as in digestion
      - fluid bathes both the inner and outer tissue layers, facilitating exchange of gases and cellular waste
- - - - ventilation- Movement of the respiratory medium over the respiratory surface maintains the partial pressure gradients of O2 and CO2 across the gill that are necessary for gas exchange
      - most gill-bearing animals either move their gills through the water or move water over their gills
      - gills often have a total surface area much greater than that of the rest of the body’s exterior
      - f gas exchange is maximized by countercurrent exchange, the exchange of a substance or heat between two fluids flowing in opposite directions
      - Gills are outfoldings of the body surface that are suspended in the water
      - Lungs
      - Gills
      - localized respiratory organs
      - an infolding of the body surface, they are typically subdivided into numerous pocket
      - not in direct contact with all other parts of the body, the gap must be bridged by the circulatory system, which transports gases between the lungs and the rest of the body
      - Lungs have evolved both in organisms with open circulatory systems
- - - - Ex-Arthropods, such as grasshoppers, and some molluscs
      - Closed circulatory system
      - Circulatory fluid- called hemolymph, is also the interstitial fluid that bathes body cells
      - circulatory fluid- called blood is confined to vessels and is distinct from the interstitial fluid
      - open circulatory system
      - One or more hearts pump blood into large vessels that branch into smaller ones that infiltrate the tissues and organs
      - Carries the oxygen-rich blood to all parts of the body
      - . Chemical exchange occurs between the blood and the interstitial fluid, as well as between the interstitial fluid and body cells
      - Functionally connects the aqueous environment of the body cells to the organs that exchange gases, absorb nutrients, and dispose of wastes
      - Ex- Annelids (earthworms), cephalopods (including squids and octopuses), and all vertebrates have closed circulatory systems
      - Components- a circulatory fluid, a set of interconnecting vessels, and a muscular pump, the heart
- - - - Veins- carry blood back into the heart
      - Atria- the chambers of heart that receives blood
      - capillaries converge into venules, and venules converge into veins, the vessels that carry blood back to the heart.
      - Ventricles- responsible for pumping blood out of the heart
      - Arteries branch into arterioles. These small vessels convey blood to capillaries,
      - Single Circulation
      - Arteries carry blood from the heart to organs throughout the body
      - blood travels through the body and returns to its starting point in a single circuit (loop)
      - Arteries, veins, and capillaries are the three main types of blood vessels
      - examples- sharks, rays, and bony fishes
      - cardiovascular system is often used to describe the heart and blood vessels in vertebrates
      - heart that has two chambers: an atrium and a ventricle
      - Blood entering the heart collects in the atrium before transfer to the ventricle. Contraction of the ventricle pumps blood to a capillary bed in the gills
      - Double Circulation
      - Two circuits of blood flow (parallel circuit) the pumps for the two circuits are combined into a single organ, the heart
      - The right side of the heart- pulmonary circuit- pumps oxygenpoor blood to the capillary beds of the gas exchange tissues
      - systemic circuit- begins with the left side of the heart
      - pumping oxygen-enriched blood from the gas exchange tissues to capillary beds in organs and tissues throughout the body
      - blood pressure is often much higher in the systemic circuit than in the gas exchange circuit
- - - - changing the air pressure within its lungs relative to the pressure of the outside atmosphere
      - pulling, rather than pushing, air into their lungs
      - Negative pressure breathing
      - Expanding the thoracic cavity during inhalation involves the animal’s rib muscles and the diaphragm
      - inflating the lungs with forced airflow
      - begins when muscles lower the floor of an amphibian’s oral cavity, drawing in air through its nostrils
      - positive pressure breathing
      - Contracting the rib muscles pulls the ribs upward and the sternum outward
      - the nostrils and mouth closed, the floor of the oral cavity rises, forcing air down the trachea
      - . At the same time, the diaphragm contracts, expanding the thoracic cavity downward
      - descending movement of the diaphragm that is analogous to a plunger being drawn out of a syringe
- - - - A compact organ-functions in both osmoregulation and excretion
      - consist of tubules arranged in a highly organized manner and are closely associated with a network of capillaries
      - The excretory tubules carry and process a filtrate produced from the blood entering the kidney
      - remaining fluid leaves the excretory tubules as urine, is collected in the inner renal pelvis, and exits the kidney via the ureter.
      - Nearly all of the fluid in the filtrate is reabsorbed into the surrounding blood vessels and exits the kidney in the renal vein
    - - Urine produced by each kidney exits through a duct called the ureter, They drain into the urinary bladder
    - - Sac which stores urine. the two ureters drain into a common sac called the urinary bladder
    - - urine is expelled from the bladder through a tube called the urethra,
- - - - Reabsorption in the proximal tubule is critical for the recapture of ions, water, and valuable nutrients from the huge volume of initial filtrate
      - Processing of filtrate in the proximal tubule helps maintain a relatively constant pH in body fluids
      - As the filtrate passes through the proximal tubule, materials to be excreted become concentrated. Many wastes leave the body fluids during the nonselective filtration process and remain in the filtrate while water and salts are reabsorbed
    - - the first portion of the loop, the descending limb, numerous water channels formed by aquaporin proteins make the transport epithelium freely permeable to water
      - the filtrate loses water and increases in solute concentration all along its journey down the descending limb
      - further reduces filtrate volume via distinct stages of water and salt movement
    - - plays a key role in regulating the K+ and NaCl concentration of body fluids
      - regulation involves variation in the amount of K+ secreted into the filtrate as well as the amount of NaCl reabsorbed from the filtrate
      - The distal tubule also contributes to pH regulation by the controlled secretion of H+ and reabsorption of HCO3