Topic 3

• Why are Microorganisms able to perform exchange via their surface?

  • have a large surface area to volume ratio

  • have a short diffusion distance

  • have low demand
• How do Microorganisms Obtain Nutrients & Remove Waste?

  • by exchange via their surface

  • nutrients (e.g. glucose, oxygen) move in by diffusion via their surface

  • waste (e.g. carbon dioxide) move out by diffusion via their surface
• Why can't Animals/Plants perform exchange via their surface?

  • have a small surface area to volume ratio

  • multicellular (large diffusion distance and high demand)

  • impermeable surface (prevent pathogens entering and reduce water loss)

  • therefore, require specialised Exchange & Transport systems

  • exchange system = increases rate of diffusion of nutrients in and wastes out

  • transport system = deliver nutrients and remove waste from all cells
• Why do Fish have Specialised Gas Exchange Systems?

  • multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand & body surface impermeable

  • therefore, cannot perform gas exchange (O2 in/CO2 out) via their surface, they require a specialised gas exchange system called Gills

  
• Structure of Gills in Fish?

  • many gill filaments and gill lamellae = large surface area

  • gill lamellae have a thin wall (short diffusion distance) and are permeable

  • ventilation brings in pure water (high oxygen, low carbon dioxide) and circulation brings in deoxygenated blood (low oxygen, high carbon dioxide), the water and blood pass over in opposite directions (countercurrent flow), which maintains concentration gradient all the way along the gill lamellae
• Why do Insects have Specialised Gas Exchange Systems?

  • multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand & body surface made of exoskeleton (impermeable barrier to reduce water loss)

  • therefore, cannot perform gas exchange (O2 in/CO2 out) via their surface, they require a specialised gas exchange system called Tracheal System

  
• Structure of Tracheal System in Insects?

  • starts with openings on body surface called Spiracles

  • spiracles contain valves, open = gas exchange, closed = prevent water loss

  • spiracles connect to Trachea

  • trachea connect to Tracheoles

  • tracheoles connect directly to Respiring Cells (delivering oxygen, removing carbon dioxide)

  
• How does Gas Exchange occur in Tracheal System of Insects?

  • at rest = down a concentration gradient, oxygen moves in & carbon dioxide moves out by simple diffusion

  • when active = by ventilation, air inhaled for mass flow of O2 in & air exhaled for mass flow of CO2 out
• Function of Lungs?


  site of gas exchange in mammals (oxygen into blood - used in cells for respiration,

  • carbon dioxide out of the blood - toxic waste product of respiration)

  
• What is Lungs made up of?

  Trachea, Bronchi, Bronchioles, Alveoli (+ capillaries)
• Function of trachea, bronchi, bronchioles?


  transport of air and filter air, (bronchioles also controls amount of air reaching alveoli)

  
• Structure of trachea/bronchi?


  • wall made of c-shaped cartilage

  • cartilage is strong so trachea/bronchi do not collapse

  • cartilage is c-shaped to give flexibility

  • lining made of goblet cells and ciliated epithelial cells

  • goblet cells make mucus, which traps pathogens/particles

  • ciliated epithelial cells have cilia, which pushes mucus up and out of lungs
• Structure of bronchioles?


  • wall made of smooth muscle

  • smooth muscle contracts, lumen narrows, bronchiole constricts

  • (occurs when surrounded by noxious gases - reduces amount reaching alveoli)

  • lining made of goblet cells and ciliated epithelial cells

  
• Adaptation of alveoli?


  • millions of tiny alveoli that are folded (large surface area)

  • thin wall/one cell thick/squamous epithelial cells (short diffusion distance)

  • elastic tissue in wall (stretches when breathing in to increase surface area, recoils when breathing out to push the air out)

  • ventilation maintains concentration gradient (high oxygen, low carbon dioxide)

  
• Adaptation of capillaries?


  • millions of tiny capillaries (large surface area)

  • thin wall/one cell thick/squamous epithelial cells (short diffusion distance)

  • narrow lumen (increases diffusion time, decreases diffusion distance)

  • circulation maintains concentration gradient (low oxygen, high carbon dioxide)

  
• How O2 moves from the alveoli to the capillaries?

  by simple diffusion passing thru the alveolar epithelium and capillary epithelium
• How CO2 moves from capillaries to the alveoli?

  by simple diffusion passing thru the capillary epithelium and alveoli epithelium
• Describe the process of Breathing/Ventilation?

  • Breathing In/Inhalation = external intercostal muscles contract (rib cage moves up and out) & diaphragm contracts (flattens), therefore increase in volume in chest and decrease in pressure, so air moves in

  • Breathing Out/Exhalation = external intercostal muscle relax (rib cage moves down and in) & diaphragm relaxes (back to dome shape), therefore decrease in volume in chest and increase in pressure, so air pushed out (aided by elastic recoil in the alveoli)

  
• Formula for Pulmonary Ventilation?

  • PV = tidal volume x ventilation rate

  • tidal volume = volume of air breathed in/out in one breath

  • ventilation rate = number of breaths per minute

  • Pulmonary Ventilation = volume of air breathed in/out per minute
• Function of Intestines?


  site of exchange of digested nutrients in mammals
• What is Digestion?


  1. Breakdown of Large Insoluble Molecules into Small Soluble Molecules (so they can move into the blood and then into the body cells)

  2. Starch/Glycogen = (Carbohydrates) into Glucose - by Amylase (Salivary in mouth, Pancreatic in small intestine) and Maltase - Lactase - Sucrase (on lining of small intestine)

  3. Proteins = into Amino Acids by Endopeptidase - Exopeptidase- Dipeptidase (Endopeptidase in stomach, Exopeptidase in small intestine, Dipeptidase on lining of small intestine)

  4. Lipids = into Monoglyceride and 2 Fatty Acids by - Lipase (in small intestine)
• What do Intestine Absorb?

  • Small Intestine absorbs small soluble nutrients (glucose, amino acids, monoglyceride and fatty acid, vitamins and minerals)

  • Large Intestine absorbs water
• Why do Humans/Mammals require a Specialised Transport System?

  • multicellular organisms therefore have large diffusion distances and high demand

  • need a transport system to deliver nutrients and remove waste from all cells

  • transport system in humans/mammals called Circulatory System

  • Circulatory System made of heart, blood vessels, blood

  • (heart pumps blood, blood vessels carry blood, blood carries nutrients/waste)
• Why is the transport system in mammals called a double circulatory system?

  • the heart pumps twice, the blood goes through the heart twice - generates enough pressure to supply all body cells
• Why is the transport system in mammals called a closed circulatory system?

  • blood is transported in blood vessels - helps to maintain pressure and redirect blood flow
• Layout of Circulatory System?

  • heart pumps blood which is carried in arteries which flow into arterioles which flow into capillaries which then are carried in venules then veins back to the heart

  • Artery to Arterioles to Capillaries to Venules to Veins

  • Artery/Arterioles carry blood away from the heart

  • (arterioles are small arteries)

  • Capillaries are the site of exchange (nutrients out, waste in)

  • Veins/Venules return blood back to the heart

  • (venules are small veins)

  
• Heart?


  • job is to pump blood around the body (delivers nutrients to cells and remove waste)

  • made of 4 muscular chambers (2 atria, 2 ventricles)

  • atria pumps blood to ventricles, ventricles pump blood out of heart (R to lungs, L to body)

  • ventricles thicker then atria (has to pump blood further)

  • left ventricle has a thicker muscular wall then right ventricle, therefore has stronger contractions, so can generate higher pressure and pump the blood further around the body

  
• Blood vessels of the heart?

  • artery takes blood away from the heart, vein returns blood to the heart

  • Vena Cava supplies R atrium (with deoxygenated blood from body)

  • Pulmonary Vein supplies L atrium (with oxygenated blood from lungs)

  • R ventricle supplies Pulmonary Artery (deoxygenated blood to lungs)

  • L ventricle supplies Aorta (oxygenated blood to body)

  
• Job of valves in heart?

  • Ensure one way flow of blood, no backflow

  • (blood flows from atria to ventricles to arteries)

  • 2 sets of valves: Atrio-ventricular Valve & Semi-lunar Valve

  • AV valve = between atria and ventricles

  • SL valve = between ventricles and arteries
• When are AV valves open or closed?

  Open = pressure in atria greater then pressure in ventricles, Closed = pressure in ventricles greater then pressure in atria
• When are SL valves open or closed?

  Open = pressure in ventricles greater then pressure in arteries, Closed = pressure in arteries greater then pressure in ventricles
• cardiac cycle


  • Atria Contracts, ventricles relax = atrial systole

  • Ventricles Contract = ventricular systole

  • Filling Stage, both relaxed = diastole

  
• atrial systole


  • contraction of the atria

  • atria contract, and the pressure in them increases

  •ventricles are relaxed, w/ lower pressure
• ventricular systole


  • Contraction of ventricles

  • Atrioventricular valves (mitral and tricuspid)

  close = "Lub" sound

  • pressure will rise in the ventricles, pushing blood out of the ventricles + opening semi-lunar valves

  • muscles will relax pressure decreases and semi-lunar valves close - "dub" sound
• diastole


  • the relaxation phase of the heartbeat; the period of least pressure

  • the heart is filled w blood and both muscles are relaxed

  • the AV valves open because of increased pressure in atria than ventricles

  •semi lunar valves close
• What causes the Heart Sounds?

  • when the valves close

  • 1st = AV closes

  • 2nd = SL closes
• Formula for Cardiac Output?


  • CO = Stroke Volume x Heart Rate

  • stroke volume = volume of blood pumped out of the heart in one beat

  • heart rate = number of beats per minute

  • Cardiac Output = volume of blood pumped out of the heart in one minute
• Coronary Heart Disease and Myocardial Infarction?

  • high blood pressure damages lining of coronary artery

  • fatty deposits/cholesterol builds up beneath the lining, in the wall = Atheroma

  • the atheroma breaks thru the lining forming a Atheromatous Plaque on the lining, in the lumen

  • this causes turbulent blood flow

  • a blood clot (thrombus) forms

  • this block the coronary artery

  • therefore less blood flow to the heart muscle

  • less glucose and oxygen delivered

  • the heart muscle cannot respire

  • so it dies (myocardial infarction)
• Risk Factors of CHD?

  • Age, gender, ethnicity

  • Saturated fats (increases LDL, LDL deposits cholesterol in the arteries to form atheroma)

  • Salts (increases blood pressure - lowers water potential of the blood so it holds the water)

  • Smoking (nicotine = increase HR and makes platelets more sticky - blood clot, carbon monoxide = permanently blocks haemoglobin)

  • Obesity and Lack of Exercise
• Atheroma & Aneurysm?


  atheroma weakens wall of artery, blood builds up in the wall, the wall swells then bursts = aneurysm