Functional histopathology of the CV system Flashcards
Circulatory system functions
transport of oxygen and nutrients to the tissues
transport of carbon dioxide and other metabolic waste products from the tissues
involved in temp regulation
distribution of molecules (hormones) and cells (immune system)
What are the 2 functional components of the circulatory system?
blood vascular system
lymph vascular system
Arteries function
efferent vessels to carry blood and nutrients and oxygen to tissues
Capillaries function
complex network of thin tubules, interchange between blood and tissues takes place
Veins function
convey the blood back towards the heart to be pumped again
Describe the tunica intima
inner lining comprising a single layer of flattened epithelial cells (endothelium)
supported by basement membrane and collagenous tissue
Describe the tunica media
intermediate muscular layer
smooth muscle and elastic fibre layer regulated by sympathetic nervous system
controls vasoconstriction/vasodilation of vessels
Describe the tunica adventitia/externa
an outer supporting tissue
collagen fibres protect and support vessels
larger vessels contain vaso vasorum
What is the vaso vasorum?
Small blood vessels that supply the walls of larger arteries and veins
Define endothelium
single layer of squamous epithelium, lining the internal surfaces of all components of the blood and lymphatic systems
Describe the functions of the endothelium
selective permeable anthrombotic barrier
determines when and where white blood cells leave circulation for the interstitial space of tissue
secretes paracrine factors for vessel dilation, constriction and growth of adjacent cells
Name some large elastic arteries
aorta and its large branches (innominate, subclavian, common carotid and iliac)
pulmonary arteries
What happens in elastic arteries during systole and diastole?
high content of elastic fibre so media expands during systole and stores some of the energy of each heartbeat
elastic recoil of the vascular wall during diastole propels blood through the more distal vessels
Describe elastic (conducting) arteries
large lumen allow low resistance conduction of blood
contain elastin in all 3 tunics
withstand and smooth out large blood pressure fluctuations
allow blood to flow fairly continuously throughout the body
Describe muscular arteries
tunica intima has endothelial lining and some connective tissue
thicker tunica media than vein and narrower lumen and thicker elastic laminae
more smooth muscle and less elastin in tunica media than elastic arteries
Describe the structure of arterioles
tunica intima is continuous endothelium and thin subendothelial layer
generally tunica media has 2 layers of smooth muscle cells
(smallest arterioles = 1 layer)
tunica adventitia = thin sheath of connective tissue
Describe the structure of capillaries
just big enough for single file erythrocytes
single layer of endothelial cells surrounded by basement membrane
some have tissue specific functions
Universal functions of capillaries (not tissue-specific)
oxygen and nutrient delivery to tissues
carbon dioxide and nitrogenous waste removal
Where are continuous capillaries present?
muscle
lungs
central nervous system
Where are fenestrated capillaries present?
endocrine glands
sites of metabolic and fluid absorption (eg. gallbladder, kidney and intestinal tract)
Where are discontinuous (sinusoidal) capillaries present?
liver
spleen
bone marrow
Describe continuous capillaries
have endothelial cells that provide an uninterrupted lining
What are the 3 types of capillaries?
continuous
fenestrated
discontinuous/sinusoidal
Describe fenestrated capillaries?
endothelium riddled with pores
greater permeability to solutes and fluids than other capillaries
Describe sinusoidal capillaries
highly modified, leaky, fenestrated capillaries with large lumens
discontinuous layer of endothelial cells with wide spaces between
basal lamina is discontinuous
allow large molecules (proteins and blood cells) to pass between blood and surrounding tissues
Veins function and how are they classified?
collect blood from all tissues and organs and return it to the heart
classified by size:
- venules
- medium-sized veins
- large veins
How does blood return to the heart in veins?
contraction of tunica media
external compressions from surrounding muscles
Where do valves project from and what is their function?
project from the tunica intima
prevent backflow of blood
What are the special features of veins?
veins contain valves (prevent backflow of blood, most abundant in legs where blood has to travel against gravity)
muscular contraction (aids return of blood to heart in conjunction with valves)
Compare arteries and veins (lumen, thickest layer, tunica intima)
artery = narrow lumen, thicker tunica media, intima separated from media by internal elastic lamina
vein = larger lumen, tunica externa is thickest, tunica intima is folded to form valves)
What are the 3 tunics of the heart wall?
internal = endocardium
middle = myocardium
external = pericardium
What is the function of the fibrous central region of the heart (fibrous skeleton)?
serves as a base of the valves
site of origin and insertion of cardiac muscle cells
electrical insulator between atria and ventricles
List the electrical pathway of the heart
sinoatrial node
atrioventricular node
bundle of his
left and right bundle branches
purkinje fibres
Where is the sinoatrial node located and what is it’s function?
pacemaker of the heart
located near the junction of the right atrial appendage and the superior vena cava
Where is the AV node located and what is it’s function?
located in the right atrium along the atrial septum
delays transmission of signals from atria to ventricles - ensures that atrial contraction precedes ventricular contraction
Where is the bundle of his located?
courses from right atrium to the summit of the ventricular septum
