Medicine Core Block - Anatomy -The Heart And The Lymphatic System - UCLan
The Heart
Circulation from the heart
Structure: Three layers (tunica): Intima, Media, and Adventitia. Different thicknesses of layers in vessels, most distinct in arteries. Veins have different sizes, arteries have muscular specializations and capillaries can only fit 1 blood cell at a time.
Great Vessels:
- Superior Vena Cava: Drains deoxygenated blood from the thorax, upper limbs, head, neck, and brain.
- Inferior Vena Cava: Drains deoxygenated blood from the abdomen and lower limbs.
- Aortic Arch: Supplies the entire body with oxygenated blood.
- Pulmonary Track: Takes deoxygenated blood from the heart to the lungs to be oxygenated.
- Pulmonary Veins: Leave the lungs carrying oxygenated blood and deliver it to the heart ready to be circulated around the body.
Coronary Circulation: Refers to the oxygenated blood sent to the heart for functional purposes. The left and right coronary arteries form the coronary sulcus that branches around the interventricular sulci converging to the apex of the heart. These drain through the cardiac veins emptying into the right atrium.
Conduction: The SA Node sends impulses to;
- Internodal Tracts: Stimulate contraction of the right atrium
- Bachmann’s Bundle: Stimulate contraction of the left atrium
- AV Node: Passing signals to the ventricles
- Bundle of His: Splits into right and left branches that continue to Purkinje fibers.
Cardiac Cycle:
- Systole: The period of contraction that the heart undergoes while it pumps blood.
- Diastole: The period of relaxation that occurs as the heart chambers fill with blood.
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Lymphatic System:
Lymphatic System: A series of organs, vessels, and nodes that collect and filter excess tissue fluid (lymph) before returning it to the venous circulation
Function:
- Drains excess interstitial fluid from tissues into the venous system
- To produce and transport immune cells (lymphocytes) that will mount an immune response against pathogens.
- To transport dietary lipids from the GI tract into the blood.
Drainage: Lymph drains back into venous circulation near the heart. However, the duct via which it drains depends on where in the body the lymph is.
- Thoracic Duct: Collects lymph from the left head, neck, thorax, upper limb, and lower half of the body (40 cm long)
- Right Lymphatic Duct: Collects lymph from the right head, neck, thorax, and upper limb (1cm long)
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