Circulatory system Flashcards
What are the two related systems of the circulatory system
The cardiovascular system and lymphatic vascular system
What does the cardiovascular system consist of
Heart, arteries, capillaries and veins
Roles of the cardiovascular system
- Transport oxygen and nutrients to the tissue
- Transport CO2 and other metabolic waste from the tissue
- Temperature regulation
- Distribution of hormones and immune cells
- Penile erection
Where is the blood within the body found
65% in peripheral veins, 20% in heart and lungs, 10% in peripheral arteries and 5% in capillaries
What are the 3 laters to a blood vessel
Tunica intimate, tunic media and tunica adventita
Tunica intimate
- Inner layer
- Single layer of squamous epithelial cells termed endothelial cells
- Supported by a basal lamina and a thin layer of connective tissue
Tunica media
- Middle layer
- Made up predominantly of smooth muscle
- Thickness of this layer varies
Tunica adventita
- Outer layer
- Made of supporting connective tissue
What separates the tunica intimate from the tunica media
Internal elastic membrane
What is separates the tunica media from the tunica adventita
External elastic membrane
What are the largest arteries termed and why
Elastic arteries because they have many sheets of elastic fibres in their tunica media to provide elastic recoil
Some vessels need their own vascular supply and this is known as the
Vasa vasorum
Arterioles
- Only have one or two layers of smooth muscle in their tunica media
- Almost no adventita
- Important in controlling blood flow
Composition of capillaries
- Composed of endothelial cells and basal lamina
- Have pericytes at intervals outside basal lamina
Pericytes
Connective tissue cells that have contractile properties
Different types of capillaries
Continuous, fenestrated and sinusoidal/discontinuous
Continuous capillaries
- Most common
- Found in muscle, connective tissue, lung, skin and nerves
Fenestrated capillaries
- Have pores in the walls
- Found in the mucosa of the gut, endocrine glands, and the glomeruli of the kidney
Sinusoidal/discontinued capillaries
- Lack a basal lamina
- Have large gaps through which macromolecules and cells can pass through
- Found in liver, spleen and bone marrow
What do capillaries form
Networks
What are microvascular networks made up of
Small arterioles connecting to a postcapillary venule, through a network of met arterioles, thoroughfare channels, and capillaries
What helps control the flow through the capillary network
Precapillary sphincters
Veins
- Relatively thin but continuous tunica media
- Have a thick tunica adventitia
- Flexible and can accommodate expansion
Three layers of the heart
Endocardium, myocardium and epicardium
Endocardium
- Lines the entire inner surface of the heart
- Composed of endothelium, basal lamina, a thin layer of collagen fibres, and a layer of dense connective tissue
- In some areas there is subendocardium of loose connective tissue containing small blood vessels and nerve and the branches of the the impulse connecting system
Myocardium
- Thick middle layer
- Bundles and layers of contractile cardiac muscle fibres
- Individual fibres are surrounded by delicate, collagenous connective tissue with a rich network of capillaries
Epicardium
- Outer layer of the heart
- A single layer of flattened epithelium called mesothelium
- Basal lamina
- Fribroelatsic connective tissue and in spaces adipose tissue
What is embedded within the adipose tissue on the surface of the heart
Coronary vessels
What are the two parts of the pericardium
Fibrous pericardium and serous pericardium
Fibrous pericardium
Is a sac of tough fibrocollagenous connective tissue
Serous pericardium
Made up of a layer of simple squamous epithelium, backed by a basal lamina and connective tissue
What is between the fibrous and serous pericardiums
Pericardial cavity
What is contained within the pericardial cavity
Pericardial fluid
What is the action of pericardial fluid
To provide lubrication for the heart
What is the fibrous skeleton of the heart made of
Fibrous connective tissue
Functions of fibrous skeleton of the heart
- Support the valves
- Provides attachment for cardiac muscle fibres
Heart valves
- Outer endothelial layer with a basal lamina
- Layer of collagen and elastin fibres
- A core of dense connective tissue
- Anchored to papillary muscles in the wall of the ventricle by chordae tendinae
- No blood vessels
What is the core of dense connective tissue in the heart valves known as
Lamina fibrosa
What are the 3 types of cardiac muscle cells
Contractile cells, pacemaker cells and conducting cells
Pacemaker cells
- Highly specialised muscle cells
- Embedded in an extensive matrix of connective tissue
- Have few myofibrils, little glycogen and no proper T-tubule system
At the junction of the atria and vntricles, what picks up the depolarisation
the AV node
From the AV node where do electrical impulses travel
Down the interventricular septum via AV bundle, then through the left and right bundle branches to the apex of heart and then they contact the Purkinje fibres
What electrically isolates the atria from the ventricles
The fibrous skeleton
Purkinje fibres
- Larger than normal cardiac muscle cells
- Found in the sunendocaridal layer just deep to endocardium
- Abundant glycogen, no T-tubules, no intercalated discs and sparse actin and myosin
- Distribute excitatory activity
In which way does excitation pass through the ventricles
Inferiorly to superiorly
