Week 7 Circulatory system Flashcards
Pericardium
Covering of the heart
- Outer fibrous sac
- inner serous layer (secretes slippery fluid to prevent friction
Epicardium
- Thin layer of connective tissue
-Contains fat
-
Myocardium (muscle heart)
- Thick cardiac muscle walls
- cardiomyocytes
Cardiac muscle build
- Striated
- Involuntary
- Branched
- 1-2 Nuclei
- intercalated discs
Endocardium (inside the heart)
- Innermost surface that lines heart chambers
- Endothelium continuation of blood vessels
- Simple squamous epithelium (flattened)
Chamber of the heart
- Left and right Atria
- Left and right Ventricles
- Cardiac septum
The atria
(Atrium = entryway) Are receiving chambers • Relatively small, thin walled • Minimal contraction Right Atria • Blood enters via 3 veins: • Superior vena cava • Inferior vena cava • Coronary sinus Left Atria • Blood enters via 4 pulmonary veins • Fossa ovalis
The ventricles
(ventr = underside) • Discharging chambers ie pumps• Majority of heart volume• Trabeculae carneae Right Ventricle • To pulmonary trunk Left Ventricle • to body via aorta
Patent ductus arteriousus (PDA)
The ductus arteriosus is a normal foetal blood vessel that closes soon after birth
• vessel does not close a• remains “patent“
• irregular mixing of oxygenated and deoxygenated blood
between two of the most
important arteries
• the aorta
• pulmonary artery
Valves of the heart
Atrioventricular (AV) Valves Cuspid = pointed • Right: tricuspid (3 cusps) • Left: bicuspid/Mitral (2 cusps)
Semilunar (SL)valves
• Semilunar = half moon
• Right: pulmonary valve
• Left: aortic valve
Cardio-Pulmonary Circulation
RIGHTSIDE: Vena cavae (blood from body) Right atrium Right ventricle Pulmonary artery (blood to lungs) LEFT SIDE: Pulmonary vein (blood from lungs) Left atrium Left ventricle Aorta (blood to body)
Intrinsic
Conducting System
Sinoatrial (SA) Node • Electrical pace maker Atrioventricular (AV) Node • Receives impulses from SA Node Atrioventricular (AV) Bundle • Bundle of HIS • Electrical link between atria & ventricles Subendocardial conducting network • Purkinje Fibres • Distribute impulses to ventricles
Cardiac Pacemaker Cells
Autorhythmic • Have the ability to spontaneously depolarise • Contain special cell membrane ion channels • Are distributed throughout the intrinsic conducting system • “Fastest” cells located in SA node (75-100bpm) • The SA node sets the initial pace (called the “pacemaker”) • Ectopic pacemaker (25-40bpm)
The Electrocardiogram (ECG)
Shows currents arising from electrical activity of heart
• Recorded by electrodes placed on skin
• Size and shape varies
with electrode position• Basic features: P wave, QRS complex and T wave
The Cardiac cycle
Describes timings and mechanical events associated with blood flow through the heart that follow the electrical events Systole: • Period of ventricular contraction • Blood ejected from heart Diastole: • Period of ventricular relaxation • Blood filling ventricles of heart Blood pressure: Systolic/Diastolic
Heart function measures
Two different metrics: • Blood Pressure (BP) • Pressure created by the cardiac cycle • Measured in mm Hg 1• Heart Rate (Pulse) • The number of cardiac cycles per time • Beats per minute (bpm)
Regulation of blood pressure
Goal is to ensure appropriate tissue perfusion• Short-term
• Alter peripheral resistance & cardiac output
• Hormonal control
• Eg adrenal medulla hormones (epinephrine,
norepinephrine), angiotensin II, atrial natriuretic peptide & antidiuretic hormone (ADH)
• Long-term
• Alter blood volume
• Renal mechanisms
Regulation of Heart Rate:
Neural & Chemical
Autonomic Nervous System • Sympathetic nervous system (norepinephrine) Hormones • Epinephrine (adrenaline) • Thyroxine • Directly effects heart • Enhances effects of epinephrine Ions • Particularly Ca2+ and K+
Blood vessel structures
Consist of 3 layers (tunica)
• Tunica interna (tunica intima): thin endothelium• Tunica media: middle, smooth muscle layer
• Tunica externa (tunica adventitia): fibrous
connective tissue
Arteries vs Veins
Comparison of wall structures
Arteries • Thick tunica media (smooth muscle) walls • Contain layers of elastin fibres (elastic laminas) • No valves present
Veins • Relatively thinner walls (thinner tunica media) • Very little elastin fibres • Valves present to prevent backflow of blood • More fibrous outer layer
Major Arteries of the Human Body
Major Arteries• Aorta• Coronary
Artery• Common
Carotid Artery
Vasodilation
Widening of the lumen of a blood vessel due to relaxation of the smooth muscle within the tunica media • Increases blood flow to the tissue • Controlled by sympathetic nervous system
Vasoconstriction
Reduction in the lumen diameter of a blood vessel due to contraction of the smooth muscle within the tunica media
Decreases blood flow to the tissue
• Controlled by
sympathetic nervous system
3 basic capillary types
Capillaries are:
Site of exchange between blood and tissues
• Single endothelium layer and basement membrane
Continuous
Fenestrated
Sinusoid
The lymph nodes
- Two functions
- Cleansing the lymph
- Immune system activation
Lymph node structure
capsule
fibrous
• trabeculae
cortex densely packed follicles, • germinal centres • packed with dividing B lymphocytes • T cells in transit move through the deeper cortex
medulla
contains sinuses
• spanned by reticular fibres on
which macrophages reside
The spleen
Sits under the left side of the stomach
• Site for: – lymphocyte proliferation/immune surveillance
– storage of breakdown products of RBC’s
– storage of blood platelets (for clotting)
– reservoir for blood
The thymus
Glandular lymphoid structure • Located above the heart • Site for T-lymphocyte maturation - secretes hormones (thymopoietin and thymosin) to activate T-lymphocytes in an immune response
The tonsils
Four (4) sets of tonsils found in the human throat: 1. palatine tonsils - either side at back of throat 2. lingual tonsils - at base of tongue 3. pharyngeal tonsils (adenoids) - back of nose 4. tubal tonsils - around openings of the auditory tubes (Eustachian tubes) into the back of throat
