The Cardiovascular System (Revision) Flashcards
The Heart
Structure
- Four chambers (RA/LA/RV/LV)
- Boundaries marked by sulci
Sulci
- Contains fat and coronary blood vessels
- Coronary Sulcus: Separates the atria from the ventricles
- Interventricular Sulcus: Divides the left and right ventricles
Trabeculae Carneae
- Muscular ridges
- On the inner walls of the ventricles
- Prevent heart walls from sticking during contraction
Chordae Tendineae
- Fibrous cords
- Connect the papillary muscles to the edges of the AV valves
- Holds AV valves in place to prevent backflow
Valves
- AV valves: Tricuspid valve, bicuspid valve
- Semilunar valves: Pulmonary valve, aortic valve
- Ensure unidirectional blood flow
- Prevents backflow
Conduction System
- Heart’s rhythm is regulated by SA node
- Natural pacemaker, initiates excitation signal impulses
- Coordinates contraction of the ventricles
Pericardium
Double-walled sac enclosing the heart
Fibrous
- Outer layer
- Provides protection
- Anchors heart within thoracic cavity
Serous
- Parietal: Lines fibrous pericardium
- Visceral (Epicardium): Adheres to the heart surface
Pericardial Fluid
- In the space between the layers
- Reduces friction during heartbeat
Blood Composition
Plasma
- Liquid component
- 55% of blood volume
- Contains water, electrolytes, hormones, and proteins
Formed Elements
- 45% of blood
- Red Blood Cells (Erythrocytes)
- White Blood Cells (Leukocytes)
- Platelets (Thrombocytes)
Myocardial Ischemia
A condition caused by reduced blood flow to the heart muscle, often due to blockage in coronary arteries, leading to angina or myocardial infarction (heart attack)
Coronary Circulation
Supply oxygen-rich blood to the heart muscle
Right coronary artery
- Right Marginal Branch: Supplies lateral RA and RV
- Posterior Interventricular Branch: Supplies posterior walls of RV and LV, and interventricular septum
- Supplies SA and AV node
Left coronary artery
- Anterior interventricular branch: Supplies RV and LV, and interventricular septum
- Circumflex branch: Supplies LA and LV
Cardiac Muscle
Cardiomyocytes
- Striated, short, and thick
- One central nucleus
- Interconnect through branched ends
Electrical Signaling
- Contract in response to electrical signals
- Via gap junctions
The Cardiac Conducting System
Sinoatrial Node (SA Node)
- Located in RA
- The heart’s pacemaker
- Initiates electrical impulses at 60-100 bpm
Atrioventricular Node (AV Node)
- Receives the electrical signal from the atria
- Delays impulse (0.4 seconds)
- Allows atria to contract and fill the ventricles before transmitting the signal to the ventricles
Conducting Pathway
- SA node
- AV node
- Bundle of His
- Right and left bundle branches
- Purkinje fibres
Blood Vessel Structure
Tunica Interna
- Inner layer
- Endothelial cells
- Direct contact with blood
- Facilitates exchange
Tunica Media
- Middle layer
- Has smooth muscle and elastic fibers
- For vasodilation and vasoconstriction
Tunica Externa
- Outer layer
- Structural support
- Anchoring to surrounding tissues via collagen
Vasa Vasorum
Nutrient Supply
- Small vessels
- Supply blood to larger vessels
- Help in waste removal
Aneurysms
Definition
- Abnormal bulge
- In the wall of an artery or the heart
- Commonly in abdominal aorta and brain
- Lead to complications if ruptured
Types
- Dissecting Aneurysm: Blood accumulates between the layers of an artery, separating them
Common Causes
- Combination of atherosclerosis (buildup of fat in artery walls) and hypertension (high BP)
Arteries
Conducting Arteries
- Large arteries
- Eg aorta
- Expand and recoil with heartbeats
Distributing Arteries
- Smaller branches
- Direct blood to specific organs
Resistance Arteries
- Smaller arteries
- Regulate blood flow to tissues
Veins
Postcapillary Venules
- Smallest veins
- Receives blood directly from capillaries
Muscular Venules
- Larger than postcapillary venules
- Has more smooth muscle
Medium Veins
- Eg radial and ulnar veins
- Has valves to aid in blood return
Venous Sinuses
- Specialized spaces
- Eg coronary sinus of the heart, dural sinuses of the brain
Large Veins
- Eg venae cavae, pulmonary veins, and renal veins
Arterial Sense Organs
Carotid Sinuses
- Baroreceptors
- Located in the internal carotid artery walls
- Respond to changes in blood pressure.
Carotid Bodies
- Chemoreceptors
- Detect changes in blood composition
- Transmits signals to regulate respiration
Aortic Bodies
- Chemoreceptors
- Located on the aortic arch
- Monitor blood chemistry
Capillaries
Continuous Capillaries
- Located in most tissues
- Allows selective permeability
Fenestrated Capillaries
- Has pores that enable rapid exchange
- Located in the kidneys and intestines
Sinusoids
- Has large gaps between endothelial cells
- Allows proteins and cells to pass
- Located in the liver and spleen
Aorta and its Branches
Aorta
- Main artery from which all systemic arteries branch
Ascending Aorta
- Contains coronary arteries that supply the heart muscle
Aortic Arch
- Gives off three major branches:
- Brachiocephalic Trunk: Splits into the right common carotid and right subclavian arteries
- Left Common Carotid Artery: Supplies blood to the left side of the head and neck.
- Left Subclavian Artery: Supplies blood to the left arm
Carotid Arteries
- Common Carotid Arteries: Bifurcates into the internal and external carotid arteries
- Internal Carotid Artery: Supplies blood to the brain, eyes, and forehead
- External Carotid Artery: Supplies blood to the face and neck
