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Human Heart Respiratory System Chapter 42, Campbell, 6th edition Nancy G. Morris Volunteer State Community College Gas Exchange In Animals supplies O2 for cellular respiration disposes of CO2 (Figure 42.17) occurs between respiratory medium and organism air is 21% oxygen but the amount of dissolved O2 in water varies due to temperature, solute concentrations, etc Respiratory surface place where gas exchange with respiratory medium occurs O2 diffuses in; CO2 diffuses out surface must be wet (gases must dissolve in water) surface must be extensive enough to provide for the entire body Variation of Respiratory Surfaces entire surface – protozoa & unicellular organisms plasma membrane of each cells contacts the outside environment – sponges, cnidarians, flatworms moist skin over dense capillaries – earthworm and amphibians – must live in moist damp places to keep exchange surface moist Variation of Respiratory Surfaces most other animals lack sufficient body surface to exchange gases for the entire body they possess a region of body surface that is extensively branched or folded aquatic animals: gills are present & in direct contact with water terrestrial animals: internal respiratory surfaces that open to the atmosphere through narrow tubes: lungs & insect trachea Gills: Adaptations of Aquatic Organisms outfoldings of the body surface specialized for gas exchange -excresence Figure 42.18 some have flap-like gills that extend from each segment (annelids) localized gills on a body region where surface is subdivided to provide for large surface area (mollusks, fish) Gills must be efficient water has lower O2 concentration than air, SO fish expend a lot of energy to ventilate (increasing the flow of the respiratory medium over the respiratory surface) fish possess a unique arrangement in their gills which maximizes O2 uptake from water COUNTERCURRENT EXCHANGE – blood flows opposite to the direction in which water passes over the gills, maintaining a constant concentration gradient (Figures 42.19 & 42.20) Counter Current Mechanism Counter Current Mechanism Adaptations of Terrestrials air has advantages over water as respiratory medium: higher O2 concentration O2 and CO2 diffuse faster through air respiratory surfaces do not have to be ventilated as thoroughly disadvantage is that respiratory surface is continuously desiccated Tracheal System air enters through openings called spiracles and diffuses through small tubes extending to the surface of most cells tubes are lines with chitin some insects are so small they rely on diffusion to move O2 through the system; other rely on rhythmic body movements major reason why open circulatory system works for insects. Tracheal System Lungs highly vascularized invaginations of the body surface the circulatory system must transport oxygen from the lungs to the rest of the body land snails use an internal mantle as a lung spiders possess booklungs frogs have simple balloon like w/ limited surface area mammals have highly subdivided lungs with with a large surface area Human Respiratory System Mammalian Respiratory Systems lungs in thoracic cavity surround by the plural lining – two layers held together by the surface tension of fluid between layers air entering nostrils is filtered by cilia, warmed and moistened travels through the pharynx, through the glottis, and into the larynx (which possesses vocal cords & a voice box) Mammalian Respiratory Systems enters the cartilage-lined trachea that forks into two bronchi which further branch into finer bronchioles that dead-end in alveoli alveoli are lined with a thin layer of epithelium which serves as the respiratory surface O2 dissolves in the moist film covering the epithelium & diffuses across the capillaries covering each alveolus CO2 diffuses in the opposite direction Alveoli: SEM Ventilating the Lungs vertebrates ventilate by breathing (alternate inhalation & exhalation of air) frogs ventilate by positive air pressure – gulping air mammals ventilate by negative air pressure shallow inhalation results from contraction of the diaphragm (Figure 42.23) Respiration Ventilating the Lungs contraction of the rib muscles pulls the ribs upwards, which expands the rib cage lung volume increases, resulting in negative pressure within the alveoli, causing air to rush in exhalation occurs when diaphragm & rib muscles relax Pneumatic Lungs of Birds besides lungs, birds have 8 or 9 air sacs, which are present in the bones functions: trims body density, act as heat sinks for heat dissipation by metabolism of flight muscles, serve as bellows, to keep air moving air moves through the entire system in only one direction whether inhaling or exhaling thus providing a constant supply of oxygen Pneumatic Lungs Breathing Control breathing is automatic (thankfully!) breathing control centers of the brain 1) medulla oblongata 2) pons 10 – 14 times per minute medulla’s control center also monitors blood and cerebrospinal pH as CO2 concentrations increase, pH decreases Respiratory Pigments Oxygen transporting pigments: 1) hemocyanin – arthropods & mollusks contains copper (rather than iron) which results in blue color 2) myoglobin – a single subunit of heme 3) hemoglobin – most vertebrates found in the skeletal muscle consists of four polypeptides with central iron-containing heme which binds O2 Cooperativity the binding of O2 to hemoglobin is reversible binding of O2 to one subunit of heme changes the shape which increases the affinity of the other three subunits for oxygen the unloading of oxygen from one heme group results in conformational change that stimulates unloading from the other three Carbon dioxide transport CO2 is transported in three forms: 1) dissolved CO2 in the plasma (7%) 2) bound to the amino groups of hemoglobin (23%) 3) as bicarbonate ions in the plasma (70%) Deep-diving mammals stockpile oxygen and consume it slowly WeddellSeal