Circulation and Gas exchange

Types of circulatory systems Diffusion – oxygen and carbon dioxide, based on body shape and size Gastrovascular cavities – distribution of substances throughout the body and in digestion. Open circulatory system – arthropods, some molluscs Hemolymph, interstitial fluid, clear fluid Pumped through vessels into sinuses and back to heart Closed circulatory system – Blood confined in vessles

(a) An open circulatory system (b) A closed circulatory system Figure 34.3 (a) An open circulatory system (b) A closed circulatory system Heart Blood Heart Interstitial fluid Hemolymph in sinuses Branch vessels in each organ Pores Dorsal vessel (main heart) Figure 34.3 Open and closed circulatory systems Tubular heart Ventral vessels Auxiliary hearts

Cardiovascular system Closed circulatory system of humans Arteries – blood away from heart Capillaries – gas exchange, simple squamous tissue Veins – blood to the heart Not all arteries carry oxygenated blood and not all veins carry deoxygenated blood 2 main chambers of the heart Atrium – receiving chamber Ventricle – pumping chamber

Pulmocutaneous circuit Pulmonary circuit Figure 34.4 (a) Single circulation: fish (b) Double circulation: amphibian (c) Double circulation: mammal Pulmocutaneous circuit Pulmonary circuit Gill capillaries Lung and skin capillaries Lung capillaries Artery Heart: Atrium (A) A A A A Ventricle (V) V V Left Right Left Right Vein V Systemic capillaries Systemic capillaries Figure 34.4 Generalized circulatory schemes of vertebrates Body capillaries Systemic circuit Systemic circuit Key Oxygen-rich blood Oxygen-poor blood 5

Superior vena cava Capillaries of head and forelimbs Pulmonary artery Figure 34.5 Superior vena cava 7 Capillaries of head and forelimbs Pulmonary artery Pulmonary artery Aorta Capillaries of left lung 9 Capillaries of right lung 6 2 3 3 4 11 Pulmonary vein Pulmonary vein 5 1 10 Left atrium Figure 34.5 The mammalian cardiovascular system: an overview Right atrium Right ventricle Left ventricle Inferior vena cava Aorta Capillaries of abdominal organs and hind limbs 8 6

Pulmonary artery Aorta Pulmonary artery Right atrium Left atrium Figure 34.6 Pulmonary artery Aorta Pulmonary artery Right atrium Left atrium Semilunar valve Semilunar valve Figure 34.6 The mammalian heart: a closer look Atrioventricular (AV) valve Atrioventricular (AV) valve Right ventricle Left ventricle 7

The mammalian heart Approximately the size of a fist Made of mostly cardiac tissue Cardiac cycle – one complete sequence of pumping and filling of the heart. Systole – contraction phase of cardiac cycle Diastole – relaxation phase of cardiac cycle Cardiac output – volume of blood each ventricle pumps per minute

Valves Atrioventricular – separate the atrium from the ventricle Bicuspid – mitral valve tricuspid Semilunar valves – found at exits of the heart Pulmonary – leaving heart for lungs Aortic – leaving the heart to the aorta Lub Dup Lub – blood against the closed AV valves Dup – closing of semilunar valves Murmurs – abnormal sounds

Conduction system sinoatrial node – pace maker – sets rate and timing of cardiac muscle contraction. Atrioventricular node – conduct impulses through wall separating atrium and ventricle ECG – electrocardiogram – graph depicting stages in the cardiac cycle

Signals (yellow) from SA node spread through atria. Signals are Figure 34.8-4 1 Signals (yellow) from SA node spread through atria. 2 Signals are delayed at AV node. 3 Bundle branches pass signals to heart apex. 4 Signals spread throughout ventricles. SA node (pacemaker) AV node Bundle branches Purkinje fibers Figure 34.8-4 The control of heart rhythm (step 4) Heart apex ECG 11

Blood vessels 3 layers of tissue Endothelium – think epithelial tissue Smooth muscle Durable connective tissue Artery – arterioles – capillaries – venules - veins Arteries and veins differ slightly in structure Arteries have thicker walls due to higher pressure Veins have valves to prevent backflow

Artery Vein Red blood cells Valve Basal lamina Endothelium Endothelium Figure 34.9 Artery Vein LM Red blood cells 100 m Valve Basal lamina Endothelium Endothelium Smooth muscle Connective tissue Smooth muscle Connective tissue Capillary Artery Vein Figure 34.9 The structure of blood vessels Venule Arteriole 15 m Red blood cell Capillary LM 13

Blood pressure Arterial blood pressure is highest during systole (contraction) Pulse – rhythmic bulging of the artery walls with each heart beat. Diastole – relaxation phase, arteries go back to normal, lower pressure

Homeostasis To maintain blood pressure as best it can... Arterioles will dilate or constrict Endocrine and nervous system will produce Nitric oxide that will induce vasodilation, regulating blood pressure Gravity – you will faint to get head level to heart, increasing blood flow to brain Giraffes have higher systolic pressure, 250mmHg Lymphatic system – gains liters of fluid (lymph) a day begin lost from capillaries. Lymph nodes – contain cells that destroy bacteria and viruses.

Interstitial fluid Blood capillary Adenoid Tonsils Lymphatic vessels Figure 34.12 Interstitial fluid Blood capillary Adenoid Tonsils Lymphatic vessels Thymus (immune system) Lymphatic vessel Tissue cells Lymphatic vessel Spleen Lymph nodes Appendix (cecum) Figure 34.12 The human lymphatic system Masses of defensive cells Peyer’s patches (small intestine) Lymph node 16

Blood 55% plasma – liquid made of water, proteins, wastes, gas 45% - formed elements Erythrocytes – red blood cells Red biconcave disks No nucleus Formed in red bone marrow Leukocytes – white blood cells Immune system 5 types Thrombocytes – platelets Blood clotting

Cellular elements 45% Plasma 55% Number Constituent Major functions Figure 34.13 Plasma 55% Cellular elements 45% Number per L (mm3) of blood Constituent Major functions Cell type Functions Water Solvent for carrying other substances Leukocytes (white blood cells) 5,000–10,000 Defense and immunity Separated blood elements Ions (blood electrolytes) Osmotic balance, pH buffering, and regulation of membrane permeability Lymphocytes Basophils Sodium Potassium Calcium Magnesium Chloride Bicarbonate Eosinophils Plasma proteins Monocytes Neutrophils Albumin Osmotic balance, pH buffering Platelets 250,000–400,000 Blood clotting Fibrinogen Figure 34.13 The composition of mammalian blood Clotting Immunoglobulins (antibodies) Defense Erythrocytes (red blood cells) 5,000,000– 6,000,000 Transport of O2 and some CO2 Substances transported by blood Nutrients (such as glucose, fatty acids, vitamins) Waste products of metabolism Respiratory gases (O2 and CO2) Hormones 18

Cardiovascular disease Disorders of heart and blood vessels Cholesterol Atherosclerosis – hardening of the arteries by fatty deposits heart attack – myocardial infarction – damage or death of cardiac muscle tissue resulting from a blockage of one or more coronary arteries Stroke – death of nervous tissue in the brain due to lack of oxygen. Hypertension – high blood pressure – damages endothelium in arteries, promoting plaque build up

Gas Exchange Uptake of oxygen from the environment and the discharge of carbon dioxide to the environment Respiratory medium – conditions for gas exchange, water or air. Easier to breath in air, air is less dense and less viscous so easier to move and to force through passageways. In water, more demanding. Less dissolved oxygen in water compared to air Warmer and saltier the water, the less oxygen content. Puts higher energy expenditure on lobsters and fish

Respiration surfaces Cells that carry out gas exchange have a plasma membrane that must be in contact with an aqueous solution. Exchange takes place by diffusion, proportional to the surface area on which it occurs Hence why most respiratory organs are folded or branched

Respiratory organs Sponges, cnidarians and flatworms – cells on surface Marine worms – parapodium – flat appendages Amphibians, earthworms – skin Aquatic animals – gills Insects – tracheal system – network of tubes Amphibians (limited), most reptiles, birds and mammals depend on lungs

Branch of pulmonary artery (oxygen-poor blood) Branch of Figure 34.20 Branch of pulmonary artery (oxygen-poor blood) Branch of pulmonary vein (oxygen-rich blood) Terminal bronchiole Nasal cavity Pharynx Left lung Larynx (Esophagus) Alveoli Trachea Right lung 50 m Capillaries Bronchus Figure 34.20 The mammalian respiratory system Bronchiole Diaphragm (Heart) Dense capillary bed enveloping alveoli (SEM) 23

Mammalian respiratory system Nose – filtered , warmed, humidified, and sampled for odors Larynx Trachea – windpipe Bronchi – 2 branches Bronchioles – branches Alveoli – simple squamous – diffusion of gas exchange

Breathing Alternating inhalation and exhalation of air Positive pressure breathing – fill lungs with forced air – amphibians negative pressure breathing – pulling air into the lungs – mammals Tidal volume – volume of air inhaled and exhaled with each breath

Rib cage expands as rib muscles contract. Rib cage gets smaller as Figure 34.22 Rib cage expands as rib muscles contract. Rib cage gets smaller as rib muscles relax. Air inhaled. Air exhaled. Lung Diaphragm Figure 34.22 Negative pressure breathing Inhalation: Diaphragm contracts (moves down). 1 Exhalation: Diaphragm relaxes (moves up). 2 26

Control of breathing involuntary Nervous system – medulla oblongata mainly responsible Built in buffering system – Water reacts with water and forms carbonic acid. Carbonic acid can then dissociate into a bicarbonate ion and a hydrogen ion.

Homeostasis: Blood pH of about 7.4 CO2 level decreases. Stimulus: Figure 34.23-4 Homeostasis: Blood pH of about 7.4 CO2 level decreases. Stimulus: Rising level of CO2 in tissues lowers blood pH. Response: Signals from medulla to rib muscles and diaphragm increase rate and depth of ventilation. Carotid arteries Figure 34.23-4 Homeostatic control of breathing (step 4) Sensor/control center: Aorta Cerebro- spinal fluid Medulla oblongata 28

Respiratory adaptations of diving mammals Ex. Weddell seal of Antarctica Ability to store large amounts of oxygen Myoglobin – oxygen storing protein found in muscles. Swim with little muscle movement Blood supply to muscles can be constricted Use fermentation rather than respiration