The Mammalian Transport System AICE Biology Chapter 8 The Mammalian Transport System

Gas Exchange Basics Organisms need to exchange O2 and CO2 with the environment. Gas exchange occurs by DIFFUSION.

Basics (continued) Marine flatworm Single cells, and small organisms living in an aquatic environment can exchange gasses through body surfaces, because of large SURFACE TO VOLUME RATIO. Marine flatworm

5 1 Total surface area (height  width  number of sides  number of boxes) Total volume (height  width  length  number of boxes) Surface-to-volume ratio (surface area  volume) 6 150 125 1.2

Circulatory Systems consist of Heart – pumps blood Arteries – carry blood away from the heart Veins – carry blood back to the heart Capillaries – connect arteries to veins, allow for gas exchange with tissues

Open and closed circulatory systems Heart Hemolymph in sinuses surrounding organs Interstitial fluid Small branch vessels in each organ Anterior vessel Lateral vessels Ostia Tubular heart Dorsal vessel (main heart) Ventral vessels Auxiliary hearts (a) An open circulatory system (b) A closed circulatory system

Hearts Fish – 2 chambered heart (atrium and ventricle), one circuit Amphibians – 3 chambered heart (2 atria, one ventricle, 2 circuits (pulmonary and systemic) Reptiles – 3 chambered with some division of ventricle, 2 circuits Mammals & Birds – 4 chambered heart, 2 circuits

The Fish Heart 2 chambered heart Single circuit FISHES Systemic capillaries Gill capillaries Systemic circulation Vein Atrium (A) Heart: ventricle (V) Artery Gill circulation 2 chambered heart Single circuit Advantage: high pressure delivery to gills, high oxygenation to tissues Disadvantage: low pressure delivery to tissues

Pulmocutaneous circuit The Amphibian Heart AMPHIBIANS Systemic capillaries Lung and skin capillaries Right Left Systemic circuit Pulmocutaneous circuit A V 3 chambered heart Double circuit Pulmonary Systemic Advantage: high pressure delivery to both lungs and tissues Disadvantage: mixing of oxygenated and deoxygenated blood REPTILES

The Reptile Heart 3 chambered heart, partial ventricular separation REPTILES Systemic capillaries Lung capillaries Right Left Pulmonary circuit V A Systemic aorta Right systemic aorta 3 chambered heart, partial ventricular separation Double circuit Pulmonary Systemic Advantage: high pressure delivery to lungs and tissues Disadvantage: mixing of oxygenated and deoxygenated blood MAMMALS AND BIRDS

The Mammal Heart 4 chambered heart, complete ventricular separation MAMMALS AND BIRDS Systemic capillaries Lung capillaries Right Left Systemic circuit Pulmonary circuit V A 4 chambered heart, complete ventricular separation Double circuit Pulmonary Systemic Advantage: high pressure, high oxygenation delivery to lungs and tissues

Blood Vessels

Blood Vessels Arteries & Veins have 3 layers: Endothelium Tunica media Smooth muscle & connective tissue Tunica externa Connective tissue Capillaries, only 1 layer, the endothelium

Arteries vs. Veins High pressure Smaller diameter (narrow lumen) Thick, muscular tunica media Elastic tunica externa Low pressure Large diameter (large lumen Thin tunica media Thin, inelastic tunica externa “One way” valves

Artery Vein Basement membrane Valve Endothelium Smooth muscle Arteriole Venule Connective tissue Smooth muscle Endothelium Valve Basement membrane Capillary

Arterioles & Venules Arterioles – small arteries Venules – small veins Smooth muscle sphincters control flow to capillaries Venules – small veins

Capillaries

Blood Plasma & Lymph

Composition of Blood Plasma Water Solutes Plasma Proteins Albumen, globulins Ions Sodium, Chloride, Potassium, Calcium Glucose Amino Acids Urea

Tissue Fliud (extracellular fluid) Extracellular space, fluid forms by filtration from capillaries

Composition of Tissue Fluid (Extracellular Fluid) Same as plasma, minus most of the proteins: Water Solutes Ions Sodium, Chloride, Potassium, Calcium Glucose Amino Acids Urea

Lymph Tissue fluid is collected by a system of vessels called Lymphatic vessels. Once in the lymphatic system, the fluid is called lymph.

Lymph Circulation Unlike blood, lymph does not travel in a complete circuit Instead, lymphatic vessels have valves that only allow fluid to flow toward the heart. Lymph is “pumped” by contraction of skeletal muscles. Along the way, it is filtered through nodes. Lymph is added back to the blood at the vena cava.

A Lymph Node

Red Blood Cells Biconcave disc No nucleus in mammals Hemoglobin

B cells T cells Lymphoid stem cells Pluripotent stem cells (in bone marrow) Myeloid stem cells Erythrocytes Platelets Monocytes Neutrophils Eosinophils Basophils Lymphocytes

Hemoglobin 4 polypeptide chains Each contains an iron atom Heme group Iron atom O2 loaded in lungs O2 unloaded In tissues Polypeptide chain O2 4 polypeptide chains Each contains an iron atom Each can bind 1 oxygen molecule

Hemoglobin Dissociation Curve In this part of the graph, a small change in PO2 leads to a large change in how much O2 unloads from hemoglobin % O2 changes slowly % O2 changes

The Bohr Shift High CO2 levels create carbonic acid H2CO3 Carbonic acid releases H+ ions Hemoglobin binds H+ ions, releasing its bound O2 in the process.

The Bohr Shift pH 7.4 pH 7.2 % O2 unloaded % O2 unloaded Bohr shift

Fetal Hemoglobin Fetal hemoglobin has a higher affinity for O2 than adult hemoglobin. This facilitates O2 loading for the fetus.

Fetal hemoglobin Adult (maternal) hemoglobin

Myoglobin Found in muscles and other tissues Like hemoglobin, except only one heme and iron per molecule. Has a higher affinity for O2 than hemoglobin, facilitating the loading of O2 from the blood into the tissues

Problems With Oxygen Transport

Carbon Monoxide Carbon monoxide, CO, forms a relatively stable bond with hemoglobin, forming carboxyhemoglobin. This blocks the ability to bind oxygen. Atmospheric concentrations of .1% or higher can be fatal.

High Altitude Mt. Everest The partial pressure of oxygen falls with increasing elevation. (PO2 = 95 mm Hg) Lake Titicaca (PO2= 160 mm Hg) Sea level Percent of air that is O2 0.21  760 mm Hg (PO2 = 53 mm Hg)