Circulation and Gas Exchange Chapter 42 Notes Circulation and Gas Exchange

Circulation in Animals Diffusion alone is not enough to transport substances over long distances in animals - ex. moving O2 from the lungs to the brain The circulatory system solves this by making sure substances only diffuse a short distance

Circulation in Animals Invertebrates have a gastrovascular cavity or circulatory system for internal transport - ex. the body wall of the hydra is only 2 cells thick; the body cavity can serve for digestion and distribution

Circulation in Animals

Circulation in Animals In animals with many cell layers, gastrovascular cavities are not enough because diffusion distances are too great They will use an open or closed circulatory system - contains blood, blood vessels, and a muscular pump (heart)

Circulation in Animals In insects blood bathes the organs directly in an open circulatory system - no distinction between blood and interstitial fluid In a closed circulatory system, blood is confined to vessels and is distinct from interstitial fluid

Circulation in Animals

Circulation in Animals Humans have a closed system called the cardiovascular system - the heart has 1 atria or 2 atrium that receive blood returning to the heart - the heart also has 1 or 2 ventricles that pump blood out of the heart

Circulation in Animals - arteries, veins, and capillaries are the three main types of blood vessels - arteries are going to branch into arterioles  pass blood to the capillaries - capillary beds infiltrate each tissue; here gasses are exchanged by diffusion

Circulation in Animals Metabolic rate is an important factor in the evolution of the circulatory system - animals with high metabolic rates have more complex circulatory systems and more powerful hearts - differences are associated with gill breathing versus lung breathing

Circulation in Animals A fish heart has 2 main chambers (1 atria and 1 ventricle) - blood pumps from the ventricle to the gills; from the gill capillaries the blood moves through all other parts of the body - problem is when blood pumps through a capillary, blood pressure will drop

Circulation in Animals - this constrains the delivery of O2 to body tissues and the maximum aerobic metabolic rate of fishes Amphibians have a 3 chambered heart (2 atrium and 1 ventricle) - the ventricle pumps blood into a forked artery that splits the ventricle's output

Circulation in Animals - the pulmocutaneous circulation leads to capillaries for gas exchange - systemic circulation supplies the bodies organs with oxygenated blood - some mixing of blood occurs - reptiles have less mixing since they have a partially divided ventricle

Circulation in Animals Crocodiles, birds, and mammals have a 4 chambered heart - the left side of the heart receives and pumps oxygen-rich blood; the right side handles oxygen-poor blood - the evolution of this supported endothermic life - use 10X more energy than ectotherms

Circulation in Animals

Circulation in Animals

Circulation in Animals The mammalian heart - about the size of a closed fist - contracts and relaxes in a rhythmic cycle - cardiac cycle: one complete pumping and filling of blood

Circulation in Animals

Circulation in Animals - systole: the contraction phase - diastole: the relaxation phase Cardiac output depends on the heart rate (# of beats per min.) and stroke volume (amt. of blood pumped)

Circulation in Animals The heart has 4 valves that prevent backflow of blood - atrioventricular (AV) valve: between atrium and ventricle - semilunar valves: located at the 2 exits of the heart - the “lub-dup” sound is the of the valves closing

Circulation in Animals

Circulation in Animals - heart murmur: a defect in the heart valves when blood squirts backward The sinoatrial (SA) node or pacemaker sets the rate and timing at which cardiac muscles contract

Circulation in Animals

Circulation in Animals The lymphatic system returns fluid to the blood and aids in body defense - fluid enters the system by diffusing into tiny lymph capillaries; the systems drains back into the circulatory system Along the lymph vessel are lymph nodes: filter lymph and attack viruses and bacteria

Circulation in Animals Blood consists of several kinds of cells suspended in a liquid called plasma - blood plasma is 90% water - in the plasma are red blood cells (RBC), white blood cells (WBC), and platelets

Circulation in Animals

Circulation in Animals RBC, or erythrocytes, are the most common blood cells - main fcn. is to transport O2 - lack nuclei; leaves more space for hemoglobin - lack mitochondria; no aerobic respiration

Circulation in Animals

Circulation in Animals There are 5 major types of WBC’s or leukocytes - monocytes, neutrophils, basophils, eosinophils, and lymphocytes - monocytes and neutrophils are phagocytes Platelets are important for blood clotting

Gas Exchange in Animals Gas exchange: the uptake of oxygen and the release of carbon dioxide - don’t confuse with (cellular) respiration Respiratory medium: source of oxygen - air and water

Gas Exchange in Animals Respiratory surface: part of an animal where gases are exchanged - movement must be from diffusion - surfaces are thin w/ large surface areas - cells must be bathed in water (for plasma membrane)

Gas Exchange in Animals

Gas Exchange in Animals The structure of the respiratory surface depends on the size of the animal and whether it lives in water or on land - also influenced by metabolic demands ex. endotherms vs. ectotherms

Gas Exchange in Animals In simple animals, the plasma membrane of every cell is able to have gases diffuse in and out In other animals, their outer skin acts as a respiratory organ - animals are small and usually long and thin or flat

Gas Exchange in Animals For most other animals, the body doesn’t have enough area for gas exchange - the solution is an organ that is highly branched and folded; enlarges the surface area for gas exchange - ex. lungs, gills, and tracheae

Gas Exchange in Animals

Gas Exchange in Animals Gills are respiratory adaptations of most aquatic animals Gills are outfoldings of the body surface that are suspended in the water - total surface area of the gills is often much greater than the surface area of the rest of the body

Gas Exchange in Animals As a respiratory medium, water has advantages and disadvantages - no problem keeping the cell membranes moist - low [O2] in water Gills must be very effective to obtain enough oxygen

Gas Exchange in Animals Ventilation: increases the flow of the respiratory medium over the respiratory surface

Gas Exchange in Animals

Gas Exchange in Animals The arrangement of capillaries in a fish gill enhances gas exchange and reduces the energy cost of ventilation Countercurrent exchange: blood flows in opposite direction to the movement of water past the gills

Gas Exchange in Animals - as blood moves through the capillary, it becomes more and more loaded with oxygen. Simultaneously, it encounters water with even higher oxygen concentrations. - along the entire length of the capillary, there is a diffusion gradient

Gas Exchange in Animals

Gas Exchange in Animals Tracheal systems and lungs are respiratory adaptations of terrestrial animals Tracheal system: made up of air tubes that branch throughout the body - largest tube is called the tracheae; opens to outside

Gas Exchange in Animals - for small insects, diffusion through the trachea brings in enough O2 and removes enough CO2 to support cellular respiration - larger insects ventilate their tracheal systems with rhythmic body movements

Gas Exchange in Animals

Gas Exchange in Animals Unlike the tracheal systems that branch throughout the insect’s body, the lungs are restricted to one location - not in direct contact with all cells - the circulatory system must transport gases between the lungs and the body - size is correlated to metabolic rate

Gas Exchange in Animals Pathway of air to the lungs - the nasal cavity leads to the pharynx; when food is swallowed; the larynx moves upward and tips the epiglottis over the glottis; allows food to go to the stomach - the rest of the time the glottis is open

Gas Exchange in Animals - from the larynx, air passes into the trachea (windpipe) - the trachea forks into two bronchi, one leading to each lung - within the lung, each bronchus branches repeatedly into finer and finer tubes called bronchioles

Gas Exchange in Animals

Gas Exchange in Animals The system of air ducts looks like an inverted tree - the epithelium lining of the major branches are covered by cilia and a thin film of mucus - traps and moves dust, and pollen away from lungs

Gas Exchange in Animals At the tips of the bronchioles, there is a dead-end cluster of air sacs called alveoli - location of gas exchange across the epithelium -O2 and CO2 diffuse across the epithelium and the capillaries

Gas Exchange in Animals

Gas Exchange in Animals Ventilating the lungs - needed to maintain high [O2] and low [CO2] at the gas exchange surfaces - breathing ventilates the lungs - mammals ventilate the lungs by negative pressure breathing - pulls air instead of pushing it

Gas Exchange in Animals Lung volume increases as a result of contraction of the rib cage muscles and the diaphragm Because gas flows from high pressure to low pressure, through the nostrils and down the breathing tube to the alveoli

Gas Exchange in Animals