Animal Transport Systems

Animal Transport Systems

• Small molecules can move between cells and surroundings via diffusion
• Diffusion is only efficient over short distances as diffusion time increases proportionally to the square of the distance
• Small or thin animals facilitate the direct exchange of materials with the surrounding medium
• Most animals utilize a fluid-filled circulatory system to exchange materials with the environment

Gastrovascular Cavities

• Some animals don't have a circulatory system
• Elaborate gastrovascular cavities are present in cnidarians
• The gastrovascular cavity is involved in both digestion and substance distribution throughout the body
• The body wall enclosing the gastrovascular cavity measures just two cells thick
• Flatworms possess a gastrovascular cavity in addition to a flattened body which minimizes diffusion distances

Open and Closed Circulatory Systems

• A circulatory system has 3 components
  • Circulatory fluid
  • Interconnecting Vessels
  • A heart
• Circulatory system links cell-surrounding fluid with organs exchanging gases, absorbing nutrients, and disposing of wastes
• Circulatory systems can be open or closed, varying in the number of circuits

Hemolymph in Open Circulatory Systems

• Circulatory fluid called hemolymph directly bathes organs
• This is in insects, other arthropods, and some molluscs

Blood in Closed Circulatory Systems

• Blood remains confined to vessels and distinct from interstitial fluid
• Annelids, cephalopods, and vertebrates have closed circulatory systems

Organization of Vertebrate Circulatory Systems

• Humans and other vertebrates feature a closed cardiovascular system
• Three types of blood vessels include arteries, veins, and capillaries
• The blood moves in one direction

Vessels in Vertebrates

• Arteries branch into arterioles and carry blood away from the heart to capillaries
• Chemical exchange happens between blood and interstitial fluid
• Veins converge into venules, returning blood from capillaries toward the heart

Vertebrate Hearts

• Arteries and veins are distinguished by blood-flow direction, not oxygen content
• Vertebrate hearts have two or more chambers
• Blood enters through the atrium and is pumped out through the ventricle

Single Circulation

• Sharks and bony fishes have single circulation and a two-chamber heart
• In single circulation, blood leaving the heart goes through the two capillary beds (gill and body) before returning

Double Circulation

• Amphibians, reptiles, and mammals have double circulation
• Oxygen-rich and oxygen-poor blood are pumped separately from the right and left sides of the heart

Pulmonary Circuit

• Oxygen-poor blood flows in reptiles through the pulmonary circuit, to pick up oxygen through the lungs
• In amphibians, oxygen-poor blood flows through a pulmocutaneous circuit to pick up oxygen through the lungs and skin

Systemic Circuit

• Oxygen-rich blood delivers oxygen through the systemic circuit
• Higher blood pressure is maintained by the double circulation in organs than in single circulation

Mammalian Circulation

• Blood begins its flow with the right ventricle, and it pumps blood to the lungs via the pulmonary arteries
• Blood loads O₂ and unloads CO₂ in the lungs
• Oxygen-rich blood from the lungs enters the heart at the left atrium via the pulmonary veins
• It's pumped through the aorta to the body tissues by the left ventricle
• The aorta provides blood to the heart through the coronary arteries
• Blood flows back to the heart through vena cava from the head, neck, and forelimbs, and the inferior vena cava from trunk and hind limbs
• The superior and inferior vena cava flow into the right atrium

Blood Vessel Structure

• A vessel cavity is called the central lumen
• The epithelium that lines blood vessels is called the endothelium
• The endothelium is smooth and minimizes resistance
• Capillaries are only slightly wider than a red blood cell
• Capillaries have thin walls facilitate material exchange
• Arteries and veins have endothelium, smooth muscle, and connective tissue
• Arteries have thicker walls to withstand high pressure
• Blood flows back to the heart in the thinner-walled veins through muscle contractions

Blood Flow

• Physical laws that govern movement of fluids affect both blood flow and blood pressure
• Blood flow velocity is slowest in capillary beds due to the large cumulative cross-sectional area
• Blood flow in capillaries is necessarily slow for material exchange

Blood Pressure

• Blood flows from areas of higher to lower pressure
• Blood pressure is pressure that blood exerts in all directions
• The recoil of elastic arterial walls helps maintain blood pressure
• The resistance to blood flow dissipates pressure in the tiny capillaries and arterioles

Changes in Blood Pressure During the Cardiac Cycle

• Systolic pressure is the pressure in the arteries during ventricular systole
• Diastolic pressure is the pressure in the arteries during diastole
• A pulse is the artery wall rhythmic bulging with each heartbeat

Blood Components

• The fluid connecting the cell to its surrounding in open circulation
• A closed circulatory system contains blood
• In vertebrates, blood is connective tissue

Functions of Blood

• Blood in vertebrates is connective tissues consisting of cell suspended in a liquid matrix
• Cellular elements make up ~45% blood volume
• Blood contains inorganic salts described as electrolytes.
• Blood contains plasma proteins affecting pH and maintaining osmotic balance.
• Blood contains lipids, proteins, immunity and clotting factors.
• Blood has a higher protein concentration compared to the interstitial fluid

Cellular Elements

• Suspended in blood plasma includes 2 types of cell
  • Red blood cells (erythrocytes) transport O₂
  • White blood cells (leukocytes) function in defense
• Platelets are fragments of cells involved in clotting

Erythrocytes

• Red blood cells, or erythrocytes, are the most numerous blood cells
• Erythrocytes contain hemoglobin, an iron-containing protein that transports O₂
• A hemoglobin molecule binds up to four molecules of O₂
• Mature mammalian erythrocytes doesn’t contain a nuclei and mitochondria

Sickle Cell Disease

• Sickle-cell disease results from abnormal hemoglobin proteins that form aggregates
• These aggregates can make the erythrocytes into a sickle shape
• Sickled cells can rupture or block blood vessels

Leukocytes

• There are five major types of white blood cells (or leukocytes): monocytes, neutrophils, basophils, eosinophils, and lymphocytes
• Leukocytes work in defense by mounting immune responses against foreign substances or by destroying bacteria and clearing debris
• They are found both inside and outside of the circulatory system

Platelets

• Platelets are cell components functioning in blood clotting

Stem Cells and Cellular Element Placement

• Erythrocytes, leukocytes, and platelets develop from a common stem cell source in red bone marrow
• The hormone erythropoietin (EPO) stimulates erythrocyte production when O₂ delivery is low
• Physicians use recombinant EPO to treat anemia

Blood Clotting

• Coagulation forms solid clot from liquid blood
• Complex process leads to inactive fibrinogen converting to fibrin forming clot
• A blood clot formed within a vessel is a thrombus and impedes flow

Cardiovascular Disease

• Cardiovascular diseases are heart and blood vessel disorders
• Diseases have minor disturbances of vein or heart function and can have life-threatening disruptions of blood flow to brain / heart

Atherosclerosis

• Type of cardiovascular disease known as atherosclerosis, is caused by plaque buildup within arteries
• A player in the development of atherosclerosis is Cholesterol

Lipoproteins

• LDL (low-density lipoprotein) delivers cholesterol to cells for membrane production
• HDL (high-density lipoprotein) scavenges excess cholesterol back to the liver
• Heart disease increases for a high LDL to HDL ratio

Risk Factors in Cardiovascular Disease

• Inflammation also occurs in cardiovascular disease
• Heart attack, or myocardial infarction, is cardiac-muscle death from coronary artery blockage
• Stroke is nervous tissue death in the brain, that can result from rupture or artery blockage in or to head
• Angina pectoris is chest pain that causes partial blockage of coronary arteries

Risk Factors and Treatment of Cardiovascular Disease

• A high LDL/HDL ratio is a cardiovascular risk factor
• The proportion of LDL relative to HDL can be decreased by exercise and avoiding smoking and trans fats
• Statins reduce LDL levels and the risk of heart attacks
• Inflammation and thrombus formation affects can be an risk factors
• Aspirin inhibits inflammation can reduce the risk of heart attacks and strokes
• Hypertension, or high blood pressure, affects contribute to heart attack and stroke
• Diet, exercise and/or medication can manage/ control hypertension

Gas Exchange

• Gas exchange supplies O₂ for cellular respiration and disposes of CO₂

Partial Pressure

• Partial pressure is pressure exerted by individual gas in gas mixture
• Partial pressures also apply to gases dissolved in water
• Gases undergo net diffusion from high to low partial pressure

Respiratory Media

• Animals can have access and make media (air /water) to respiratory medium as the O₂ source
• Air is easier to obtain with O2 availability
• Animals require a different, and more efficient breathing technique
• Obtaining O₂ from water requires greater

Respiratory Surfaces

• Animals require moist respiratory surfaces since gas-exchange occurs in this state
• Gas exchange across a respiratory surface takes place by diffusion
• Respiratory surfaces including the skin, gills, tracheae, and lungs vary by animal

Gills in Aquatic Animals

• Gills are outfoldings of the body for gas exchange
• Ventilation moves the respiratory medium over the respiratory surface
• Aquatic animals move through or move water over their for ventilation

Fish Gills

• In fish gills, the countercurrent exchange system occurs where blood flows in the direction of water over gills
• Blood is less saturated with O₂ than the water it meets
• At least 80% of dissolved O₂ in is removed
• In fish gills, more than 80% of the O2 dissolved in the water is removed as water passes over the respiratory surface

Tracheal system in Insects

• Insect tracheal systems branch tubule network system that stretches length of body
• Tracheal tubes distribute O₂ to body cells
• Respiratory and circulatory systems remain separate
• Larger insects must ventilate their tracheal systems to meet O₂ demands

Lungs

• Lungs are an infolding of the body surface
• A circulatory system transports gases between the lungs and the rest of the body
• Lung size and complexity is correlated with animal metabolism

Mammalian Respiratory Systems

• A duct system conveys air to lungs
• Inhaled air is filtered, warmed, humidified and sampled
• The pharynx passes air to lungs while swallowing allows food to to stomach
• Swallowing involves the larynx upward tipping of the epiglottis blocking glottis in pharynx, blocking food from trachea

Steps in Respiration

• Air passes from pharynx, larynx, trachea through bronchi and bronchioles then reaches air sacs where gas exchange occurs
• Exhaled-air then passes vocal cords in the larynx creating sound
• The mucus lines the epithelium and move particles from ducts to the pharynx
• Muscular escalator that is involved to clean, allow to be swallowed to esophagus

Lungs

• Gas exchange occurs in alveoli sacs
• Oxygen diffuses in the capillaries
• Carbon dioxide diffuses from the capillaries and into the space

Ventilation and Breathing

• Alveoli lack cilia, making them more susceptible to contamination
• Surfactants are present to coat the alveoli's surface/lining
• Pre-term babies not having enough surfactant are vulnerable to respiratory distress syndrome is provided via surfactants
• The process that ventilates the lungs is breathing, alternate inhalation and exhalation of air

Amphibian Breathing

• Amphibians ventilate their lungs with positive pressure breathing, by forcing it to the trachea
• Bird Breathing*
• Birds have air sacs (eight or nine) that allow lungs to have air constantly
• Air goes one direction in lungs
• Both inhalation and exhalation need 2 cycles
• Birds are highly efficient

Mammalian Breathing

• Mammals ventilate their lungs with negative pressure breathing, pulling air to lungs
• The volume of the lungs that increases is rib muscles and diaphragm contracting
• Tidal volume is the volume of each with each breath
• During maximum tidal volume is referred to vital capacity
• After exhalation, there's residual volume, meaning some air is left in the lungs