bio

• Transport systems in multicellular animals

  Needed to link exchange surfaces with cells throughout the body
• Circulatory systems


  • Require a circulatory fluid, a set of interconnecting vessels, and a muscular pump (the heart)
• Types of circulatory systems


  • Open
  • Closed (cardiovascular system)
• Closed circulatory system


  The circulatory system connects the fluid that surrounds cells with the organs that exchange gases, absorb nutrients, and dispose of waste
• Order of blood vessels from the heart

  1. Capillaries

  2. Venules

  3. Arteries

  4. Veins

  5. Arterioles
• Networks of capillaries called capillary beds are the sites of chemical exchange between the blood and interstitial fluid
• Single vs Double Circulation


  Mammals have double circulation where oxygen-poor and oxygen-rich blood are pumped separately from the right and left sides of the heart
• Advantages of double circulatory system


  • Not provided
• Blood vessel structure


  Cavity is called the central lumen, epithelial layer that lines blood vessels is called the endothelium
• The endothelium is smooth
• Differences between arteries and veins


  • Artery: Thick walls, narrow lumen, valves absent
  • Vein: Thin walls, wide lumen, valves present
• Capillaries are only slightly wider than a red blood cell
• Capillary function


  Capillaries have thin walls to facilitate the exchange of materials, capillaries in major organs are usually filled to capacity
• Velocity of blood flow in capillary beds


  Slower than in arteries and veins, achieved by the large surface area of the capillary network
• Exchange at capillary beds


  Exchange between the blood and interstitial fluid takes place across the thin endothelial walls of the capillaries, driven by the difference between blood pressure and osmotic pressure
• Most blood proteins and all blood cells are too large to pass through the endothelium
• Mammalian circulation


  Blood begins flow in right ventricle, goes to lungs, returns to left atrium, pumped by left ventricle to body, returns to right atrium
• Differences between atria and ventricles


  Not provided
• Cardiac cycle


  Contraction (systole) and relaxation (diastole) phases
• The heart rate is the number of beats per minute, the stroke volume is the amount of blood pumped in a single contraction, and the cardiac output is the volume of blood pumped into the systemic circulation per minute
• Heart valves


  Atrioventricular (AV) valves separate atria and ventricles, semilunar valves control blood flow to aorta and pulmonary artery
• Some cardiac muscle cells are autorhythmic, meaning they contract without any signal from the nervous system
• Sinoatrial (SA) node


  Sets the rate and timing at which cardiac muscle cells contract
• Electrocardiogram (ECG or EKG)


  Records the impulses that travel during the cardiac cycle
• Regulation of pacemaker


  Sympathetic division speeds it up, parasympathetic division slows it down, also regulated by hormones and temperature
• Blood composition


  • Plasma (55%)
  • Cellular elements (45%)
• Plasma


  Liquid matrix containing water, ions, plasma proteins with various functions
• Cellular elements


  • Erythrocytes (red blood cells)
  • Leukocytes (white blood cells)
  • Platelets
• Erythrocytes


  Transport oxygen, contain hemoglobin, lack nuclei and mitochondria in mammals
• Hemoglobin


  Iron-containing protein that transports oxygen, binds oxygen in lungs and releases it in tissues
• Carbon dioxide transport


  Transported in blood plasma, bound to hemoglobin, release facilitated by lower pH and higher CO2 levels in tissues
• Bohr effect


  Explains why RBCs pick up and release oxygen in response to changes in CO2, pH, and temperature
• Fetal hemoglobin has a higher affinity for oxygen compared to adult hemoglobin
• Learning objectives


  • Explain the need for transport systems
  • Describe different circulatory systems
  • Explain structure and functions of blood vessels
  • Relate heart structure to function
  • Describe cardiac cycle
  • Describe how heart action is initiated and coordinated
  • Describe blood structure
  • Describe lung structure and function
  • Explain role of hemoglobin in oxygen and carbon dioxide transport
• Excretion


  Process that rids the body of nitrogenous metabolites
• Importance of removing metabolic wastes


  • Metabolic wastes must be dissolved in water to be excreted from the body
  • The type and quantity may have a large impact on water balance
• Liver


  • After the skin, the largest organ in the body
  • Average weight of 1.3 kg
  • The only human organ that is capable of natural regeneration
  • Performs many metabolic and homeostatic functions
• Formation of urea in the liver


  1. Breakdown of nitrogenous compounds releases ammonia

  2. Ammonia is rapidly removed by the liver and converted to urea
• Roles of the liver in detoxification


  • Neutralizing xenobiotics (modifying chemical constitution)
  • Inactivation and excretion of hormones such as steroids
• Kidney


  • Central to homeostasis - dispose metabolic waste and control fluid composition
  • Diverse excretory systems are variations on a tubular theme
  • Animals produce fluid waste called urine