circulation

Circulation Study Guide

Pre-Reading Assignment

  • If you do not know the answer, write: "I don't know how the circulatory and respiratory system work together to supply cells with the oxygen they need. I will find out the answer in class."

  • If you do know: write the answer.

  • Key Question: How do the circulatory and respiratory system work together to supply cells with the oxygen they need?

Circulation and Gas Exchange

  • The time taken for a substance to diffuse from one region to another is directly proportional to the square of the distance travelled.

  • Two adaptations facilitate effective gas exchange between the environment and the cells:

    1. Simple Body Plan: Organisms with minimal tissue layers aiding in diffusion.

    2. Circulatory System: A system that transports gases and nutrients.

Invertebrate Circulatory Systems

Open Circulation

  • Components: Heart, hemolymph in sinuses surrounding organs.

    • Hemolymph: The fluid in an open circulatory system analog to blood.

Closed Circulation

  • Components: Heart, small branch vessels in each organ, dorsal vessel (main heart).

    • Interstitial fluid and blood: Distinct components supporting nutrient transport.

    • Tubular heart: Structure allowing efficient flow.

Diversity of Circulatory Systems

  • Invertebrate phyla lacking a circulatory system:

    • Phylum Porifera: Sponges

    • Phylum Cnidaria: Jellyfish, corals

    • Phylum Platyhelminthes: Flatworms

    • Phylum Nematoda: Roundworms

  • These phyla rely on pseudocoel fluids for circulation.

Example Pre-Reading Assignment

  • Question: The flatworm does not have a circulatory system. How are nutrients transported through its body?

Review of Animal Phylogeny

  • Key Phyla:

    • Phy Porifera

    • Phy Cnidaria

    • Lophotrochozoa (common ancestor)

    • Eumetazoa

    • Ecdysozoa

    • Deuterostomia

  • Important Symmetry Types:

    • Radial symmetry (Porifera, Cnidaria)

    • Bilateral symmetry (other phyla)

Open and Closed Circulatory Systems

  • Open Circulatory System:

    • Structure: Heart, vessels, and body cavity vessels.

  • Closed Circulatory System:

    • Structure: Circulatory fluid remains within vessels.

  • Evolutionary Advantages:

    • Open systems: Lower hydrostatic pressure, less energy usage.

    • Closed systems: Higher hydrostatic pressure, more efficient for larger and active organisms.

Circulatory System in Mollusca and Arthropoda

  • Mollusca Components:

    1. Ostium (opening)

    2. Pericardial sinus

    3. Perivisceral sinus

    4. Aorta

  • Arthropoda Components:

    1. Pericardial sinus

    2. Perivisceral sinus

    3. Perineural sinus

  • Sinuses in Molluscs:

    • Surrounding the gills, mantle cavity, foot, stomach, kidneys.

Circulatory Systems in Annelida and Echinodermata

  • Annelida:

    • Structures: Dorsal and ventral blood vessels, hearts, pharynx, coelom, gizzard, crop, esophagus, intestine.

  • Echinodermata (Example Sea Star):

    • Water vascular system: Madreporite, stone canal, ampullae, podia (tube feet).

Vertebrate Circulatory Systems

Overview

  1. Right Atrium: Receives deoxygenated blood from body.

  2. Right Ventricle: Sends deoxygenated blood to lungs.

  3. Left Atrium: Receives oxygenated blood from lungs.

  4. Left Ventricle: Sends oxygenated blood to body.

  • Memory mnemonic: "Abraham Rode Bulls Brussels Sprouts Loaded with Vinegar"

Passage of Blood Through the Heart

  1. Right atrium receives impure blood from superior and inferior vena cavae.

  2. Right atrium contracts, blood flows into right ventricle.

  3. Right ventricle contracts, sending blood into pulmonary trunk (divides into two pulmonary arteries).

  4. Oxygenated blood via pulmonary veins comes to left atrium.

  5. Left atrium pumps blood into left ventricle.

  6. Left ventricle contracts, sending blood into the aorta.

Circulation in Fish

  • Components:

    1. Atrium

    2. Ventricle

    3. Sinus venosus

    4. Conus arteriosus

  • Single Circulation: Blood flows in a single loop from heart to gills, then to body and back to heart.

Circulation in Amphibians and Reptiles

Amphibian Circulation

  • Circulation Type: Double Circulation with a 3-chambered heart.

  • Separation: Wall separating truncus arteriosus.

Reptilian Heart and Circulation

  • Crocodilian Heart: 4-chambered heart, systemic arches:

    • Right systemic arch carries pure blood.

    • Left systemic arch carries mixed blood.

    • Differences in diameter: right is wider than left.

    • Valves: Semi-lunar valve role in circulation (closed/open states).

Limitations of Fish and Amphibian Circulatory Systems

  • Fish: Single circulation leads to low blood pressure and inefficient material and gas exchange.

  • Amphibians: Double circulation, but body receives mixed blood, generating less ATP than birds or mammals.

Most Efficient Circulation

  • Birds and Mammals:

    • 4 chambers allow complete separation of oxygenated and deoxygenated blood, more ATP produced.

    • Double circulation enables efficient material and gas exchange at high pressure.

Evolutionary Trends in Circulatory Systems

  • In Fish: A single loop suffices due to low energy needs.

  • In Amphibians: Adaptation to terrestrial life and prevention of desiccation with a double loop.

  • In Mammals: Development of 4-chambered hearts and high-pressure double circulation for ATP production and thermoregulation.

Evolutionary Variation in Double Circulation

  • Amphibians & Reptiles: Intermittent breathers with a 3-chambered heart.

  • Crocodiles: Have a 4-chambered heart, mixed systemic and pulmonary circuits.

  • Birds and Mammals: Continuous breathers with a 4-chambered heart having distinct oxygenated and deoxygenated blood.

Circulatory Structures in Different Animals

Fish Heart

  • Structure: One Atrium, One Ventricle

  • Type: Single Circulation

  • Key Feature: Gill capillaries.

Reptile/Amphibian Heart

  • Structure: Two Atria, One Ventricle (mixed oxygenated and deoxygenated blood).

  • Type: Double Circulation

  • Key Feature: Lung capillaries.

Mammalian Heart

  • Structure: Two Atria, Two Ventricles (complete separation of oxygenated and deoxygenated blood).

  • Type: Double Circulation

  • Key Feature: Lung capillaries.

Circulation in Birds and Mammals

  • Heart Structure: 4 chambered heart.

  • Type: Double circulation involving pulmonary and systemic circuits.

    • Birds: One systemic arch (right).

    • Mammals: One systemic arch (left).

  • Pre-reading assignment: How does single circulation differ from double circulation?

The Mammalian Cardiovascular System: An Overview

  • Components:

    • Superior vena cava

    • Pulmonary artery

    • Capillaries of right lung

    • Capillaries of head and forelimbs

    • Pulmonary vein

    • Aorta

    • Capillaries of left lung

    • Right atrium

    • Right ventricle

    • Inferior vena cava

    • Left atrium

    • Left ventricle

    • Capillaries of abdominal organs and hind limbs.

Structure of the Heart

  • Myocardium: Cardiac muscle tissue.

  • Pericardium: Thick membranous sac covering the heart.

  • Septum: Wall separating the right and left sides of the heart.

  • Chambers:

    • Atria: Upper chambers.

    • Ventricles: Lower chambers.

  • Valves:

    • Atrioventricular valves: Between atrium and ventricle (Left bicuspid and Right tricuspid valves).

    • Semilunar valves: Between ventricles and associated vessels (Left aortic and Right pulmonary valves).

Heart and Circulation in Birds and Mammals

  • The path of blood through the 4-chambered heart involves sequential contraction and relaxation leading to efficient circulation.

Heart Contraction and Control

  • Control Mechanism: Heartbeat is initiated by the sinoatrial (SA) and atrioventricular (AV) nodes.

    • SA Node: Located near the top of the right atrium, sending signals for atrial contraction.

    • AV Node: Located at the bottom of the right atrium, triggering ventricular contraction.

Returning Blood to the Heart through Veins

  • Mechanisms:
    A. Skeletal muscle pump: Muscle contractions aid in venous return.
    B. Respiratory pump: Pressure changes during breathing facilitate blood return.
    C. Valves: Prevent backward flow ensuring unidirectional blood flow.

Lymphatic System and Capillary Beds

  • Lymphatic System: The network of vessels through which lymph drains from the tissues into the bloodstream, playing critical roles in fluid balance and immune responses.

Diagrams and Overviews

  • Importance of visual aids in understanding blood flow and circulatory structures.

  • Diagrammatic representation of capillary, interstitial fluid, tissue cells, and lymphatic vessels essential for conceptual clarity.

Note: The guide covers comprehensive details about various aspects of the circulatory system across different animal taxa and evolutionary trends, functions, structures, and physiological processes involved in circulation, blood flow, and respiratory collaboration.