Lecture: Anatomy 6: Principles of the cardiorespiratory system Flashcards
How are heart contractions regulated?
Heart contractions are intrinsically generated and rate of is modified by autonomic nervous system (ANS).
How does the parasympathetic nervous system affect heart rate?
Decreases heart rate (Vagus nerve)
How does the sympathetic nervous system affect heart rate?
Increases heart rate
What are the 3 layers of the heart wall?
- Epicardium (visceral pericardium)
- Myocardium
- Endocardium
What is the epicardium?
Thin outer layer of heart
What is the myocardium?
Thickest inner layer of heart
What is the endocardium?
Innermost layer of heart which lines the chamber.
How does blood flow into the heart to the lungs?
Superior and inferior vena cava, right atrium, right ventricle, pulmonary artery, lungs
What are the valves in the right side of the heart?
Pulmonary valve and Tricuspid valve
How does blood flow out of the heart and around the body?
Pulmonary veins, left atrium, left ventricle, aorta, body
What are the valves in the left side of the heart?
Aortic valve and Bicuspid (mitral) valve
Describe the blood leaving the heart towards the lungs
Deoxygenated
Describe the blood leaving the heart for the body
Oxygenated
Describe the composition of cardiac muscle (myocardium)
Cardiac Muscle (Myocardium) has a striated appearance with intercalated discs (fascia adherens, desmosomes, and gap junctions). Normally mononucleated.
What are the components of the respiratory tract?
Trachea Main bronchi Secondary (lobar) bronchi (3 x right, 2 x left) Tertiary (segmental) bronchi Bronchioles Alveoli
Describe the right lung lobe
3 lobes with horizontal and oblique fissures
Describe the left lung lobe
- 2 lobes with oblique fissures
- Impression for the heart (the cardiac notch)
- Lingula; tongue-shaped region of the left lung.
Describe the composition of smooth muscle
Smooth muscle is not striated and not branching. Spindle shaped with one central nucleus per cell. Smooth muscle is under involuntary control.
Where is smooth muscle found?
Found in walls of tubular structures and hollow viscera.
What are the functions of smooth muscle?
Functions:
• Regulates diameter
• Propels liquids and solids
• Expels contents
What is the endothelium?
A monolayer of squamous (flattened) epithelial cells that covers the entire inside of the vascular system. In contact with blood.
What are the functions of the endothelium?
Functions:
• Control vascular tone and vessel diameter
• Regulate permeability
• Angiogenesis (formation of new blood vessels)
• Regulate clotting (by releasing clotting factors)
• Regulate immune response
What is an atherosclerosis?
Narrowing of arteries (myocardial infarction) or rupture of plaque causing a thrombus. Common in coronary arteries.
What is a thrombosis?
Blood clot (thrombus) e.g., rupture of atherosclerotic plaque or deep venous thrombosis.
What is an embolism?
Stray blood clot (embolism) e.g., pulmonary embolism or stroke.
What are the 3 layers of blood vessels?
- Tunica Intima
- Tunic Media
- Tunica Externa (adventitia)
Describe the structure of the tunic intima in blood vessels
Inner most layer (lined by endothelium). Composed of connective tissue which reduces friction for blood flow.
Describe the structure of the tunic media in blood vessels
Middle layer. Composed of primarily smooth muscle and connective tissue (collagen and elastin). Controls size and shape of artery/vessels.
Describe the structure of the tunic externa in blood vessels
Outer most layer. Composed of primarily collagen and contains nerves and vessels (vasa vasorum). Connects artery to surrounding structures.
What factors aid the return of blood against gravity?
- Valves
- Arteriovenous pump
- Musculovenous pump
- Respiratory pump
What are valves?
Valves are inward projection of intima, strengthened by collagen and elastic fibres.
What are the consequences of dilation of the veins?
Dilation of veins can mean valves don’t close, resulting in varicose veins.
Describe the structure of large elastic arteries (conducting)
- Large diameter (>10mm)
- Supplied by vasa vasorum; arteries are so thick that they require their own blood supply
- Tunica media contains many layers of elastin; provides force to support surges of blood flow
Describe the structure of medium muscular arteries (distributing)
- Smaller diameter (0.1mm-10mm)
- Thick layer of smooth muscle in tunica media
- Responsible for vasoconstriction, vasodilation and pulsatile contractions
Describe the structure of small arteries and arterioles (resistance)
- Narrow lumina
- Decreased thickness of all layers and tunica media is predominantly smooth muscle, 1-2 cell layers in thickness
- Tonus dictates degree of filling of capillary beds, and this dictates blood flow
Describe the structure of capillaries (exchange)
- Endothelial layer composed of only tunica initima
- Two types: continuous and fenestrated
- Function: allow exchange between blood and extracellular fluid
Describe the structure of venules
- Microscopic (8-100µm)
- Progressively increase lumen diameter
- No elastin
- Very thin tunica externa and media
- Function: drain capillary beds
Describe the structure of veins
- Under lower pressure so tunica media is thinner than arteries
- More variable
- Smaller veins are TRIBUTARIES of larger veins
- Large veins have well developed tunica adventitia/ externa
How do arteries branch into veins?
Large elastic arteries Medium muscular arteries Small arteries and arterioles Capillaries Venules Veins
What are the 2 types of capillaries?
- Continuous
2. Fenestrated (pores where more exchange takes place)
Where are fenestrated capillaries more commonly found?
Endocrine glands, the intestines, pancreas and kidney
