Exchange Systems in the Human Body Exchange systems
Exchange Systems in the Human Body
Exchange systems Every organism must exchange materials (food, waste) with its environment. Single-celled organisms employ osmosis & diffusion. Multi-cellular organisms have groups of cells with specialized functions = tissues: epithelial, nerve, etc. Organs – groups of tissues with a special purpose: heart, lung, blood, skin. Organ systems – groups of organs with a particular purpose: the circulatory system, respiratory system, urinary system, etc. Skin (an organ) protects us.
Circulatory system Every organism must exchange materials with its environment. Circulatory system connects the organs of exchange (lungs, intestines, etc. ) with the body cells. 3 main components: A circulatory fluid: (blood , hemolymph) A set of tubes (blood vessels) A muscular pump (the heart)
Circulatory system Complex animals have either open or closed circulatory systems. In an open system blood bathes the organs directly. In a closed system, blood is confined to vessels. Humans (all vertebrates) have this type of system.
Diagram of the heart
Diagram of the heart Coronary arteries supply heart muscle with oxygen and nutrients. Blockage of coronary arteries can starve the heart and cause a heart attack.
The action of the heart The four-chambered heart The two atria collect the blood, either from the lungs or from the rest of the body. The two ventricles pump the blood out of the heart.
The action of the heart Heart valves dictate a one-way flow of blood through the heart. Atrioventricular valves control flow from atria to ventricles. Semilunar valves control flow from ventricles into aorta & pulmonary artery.
The action of the heart Heart valves dictate a one-way flow of blood through the heart. The back pressure of the heart beat seals one valve as the opposite one is pushed opened.
The action of the heart Blood begins its flow with the right ventricle pumping blood through the pulmonary artery to the lungs.
The action of the heart In the lungs, the blood loads O 2 and unloads CO 2 Oxygen-rich blood from the lungs enters the heart at the left atrium and is pumped to the body tissues by the left ventricle. Blood returns to the heart through the right atrium.
Control of the heartbeat Some cardiac muscle cells can contract without any signal from the nervous system. These contractions are controlled by a region of the heart called the sinoatrial (SA) node, or pacemaker. The pacemaker sets the rate and timing of contractions.
Control of the heartbeat Maintaining homeostasis The pacemaker can monitor body conditions and adjust the heart beat to the body’s needs. The pacemaker also sends and receives signals to and from the brain stem (oldest part of brain). Within the medulla oblongata of the brain stem is the cardiac center.
Arteries, capillaries & veins The “infrastructure” of the circulatory system is its network of blood vessels: arteries, veins, capillaries. All blood vessels are built of similar tissues and have three similar layers.
Arteries, capillaries & veins Arteries carry blood away from the heart. Arteries have thicker walls that accommodate the high pressure of blood pumped from the heart
Arteries, capillaries & veins Veins return blood from capillaries to the heart. In the thinner-walled veins, blood flows back to the heart mainly as a result of muscle action
Arteries, capillaries & veins Capillaries are sites of chemical exchange between the blood and the fluid around cells.
Arteries, capillaries & veins Signals from the medulla constrict the walls of capillaries to increase or restrict blood flow. Ex: less blood to skin, more to internal organs when the body is too cold. can
Blood composition Blood is composed of plasma (55%), and solids (45%): erythrocytes, leucocytes (phagocytes and lymphocytes), and platelets.
Blood composition The following are transported by the blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea, and heat.
Exchange Systems in the Human Body
Respiratory system Ventilation: any method of increasing contact between the respiratory medium and the respiratory surface. The medium could be air (for humans) or water (fish). The respiratory surface could be lungs, gills, etc. Ventilation includes breathing, panting, gasping Hyperventilation: very fast breathing.
Respiratory system Gas exchange: the process of replacing one gas with another – to replace CO 2 in the cells or tissues with O 2. Follows the rules of physics: depends upon concentration gradients, temperature, p. H.
Respiratory system A system of branching ducts conveys air to the lungs. Air inhaled through the nostrils passes through the pharynx into the trachea, bronchioles, and dead-end alveoli, where gas exchange occurs. The process that ventilates the lungs is breathing, the alternate inhalation and exhalation of air.
Respiratory system A system of branching ducts conveys air to the lungs. The trachea, bronchi, and larger bronchioles have rings of cartilage for support. Incision for tracheostomy
Respiratory system Goblet cells of the epithelial lining of trachea, bronchi, and bronchioles and of the nose produce mucous, a viscous fluid that traps microbes and other particles. In these tissues, ciliated epithelial cells sweep mucus and trapped microbes upward, preventing microbes from entering the lungs. Contraction of smooth muscle aids coughing. H: cilia (little hairs); I: epithelial cells; J: goblet cells make the mucous; K: smooth muscle.
Respiratory system Alveolus: a dead-end, multi-lobed sac that constitutes the gas exchange surface of the lungs. Features include: large total surface area (~75 m 2), a wall consisting of a single layer of flattened cells (easier diffusion), a film of moisture (gas is dissolved), a dense network of capillaries.
Respiratory system Draw and label (inset alveoli):
Respiratory system Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs. Lung volume increases as the rib muscles (the intercostals) and the diaphragm contract.
Respiratory system Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs. Normally we breathe using just the diaphragm. The diaphragm tightens, pulls lungs down; air rushes in. For a bigger breath we tighten intercostals; they pull up, & even more air enters the lungs due to negative pressure. We breathe 9 to 20 times per minute.
Respiratory system Lung volume: Depends on many factors – For a 135 lb male, the lungs hold ~6 liters of air Only ½ L is exchanged with each breath. ~4. 8 liters of air can be forced out, leaving a residual of 1. 2 L that can’t be forced out.
Exchange systems Every organism must exchange materials with its environment. Circulatory system connects the organs of exchange (lungs, kidneys, intestines, etc. ) with the body cells. Homeostasis maintains constant conditions within the body.
Exchange Systems in the Human Body The Kidney
Urinary system The human body needs to eliminate waste material Not all food eaten is usable; ex. cell walls of plants. We don’t have the enzymes to break down cellulose. Metabolism produces toxic materials; urea (dissolved in water it becomes urine – a waste of water that limits where we live). ex.
Urinary system Organs of the urinary system include the kidneys, ureters, & bladder.
Urinary system Organs of the urinary system include the kidneys. Kidneys filter the blood to preserve a proper water and salt balance & to remove toxic matter.
Urinary system Within the kidney, nephrons clean the blood and regulate blood composition (homeostasis). A nephron
Urinary system Cleaning & regulation of blood occurs in 3 phases Filtration: in the glomerulus excess water is removed – 125 ml of blood filtered per minute.
Urinary system Cleaning & regulation of blood occurs in 3 phases Reabsorption: capillaries around the renal tubule recollect more or less water, depending on conditions.
Urinary system Cleaning & regulation of blood occurs in 3 phases Secretion: cells in the renal tubule secrete positive ions or absorb negative ions to maintain blood p. H.
Urinary system The p. H of blood (how much acid is present) is ~7. 35. The p. H of urine averages 6. 0; the urine is made from the blood plasma as it passes through the kidney, and acid was removed. The p. H scale is based on concentration; p. H 6 has 10 times more acid than p. H 7.
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