Microanatomy of the Circulatory System Flashcards
Blood Vessels
arteries, veins, and capillaries
Layers of Blood Vessels
- tunica intima
- tunica media
- tunica adventitia
Tunica Intima
composed of epithelium and internal elastic lamina. Endothelium is simple squamous composed in contact with blood.
Tunica Media
mostly smooth muscle, thickness varies with type of vessel. May have elastic fibers, may have external elastic lamina.
Tunica Adventitia
outer layer. Connective tissue (collagen) that is blue on trichrome stain. Blends with and anchors to surrounding tissue.
Components of the Tunica Adventitia
vasa vasorum, nervi vasorum, adipose tissue
Vasa Vasorum
small vessels that supply large vessels
Nervi Vasorum
nerve supply to large blood vessels.
Arteries
high pressure vessels that take blood away from the heart
Types of Arteries
elastic arteries, muscular arteries, and arterioles
Elastic Arteries
aorta and largest branches. Tunica media contains lots of elastic fibers that are squiggly bright pink fibers. Cells between elastic fibers are smooth muscle
Muscular Arteries
medium-sized arteries. Tunica media is muscular. Very common
Arterioles
less than 3 layers of smooth muscle cells. Small diameter. Innervated by sympathetic nervous system. Regulate blood flow into capillaries via capillary sphincter
Capillaries
consist of endothelium and basement membrane only. No muscle. almost every cell in the body has a capillary nearby. Erythrocytes are often single file
What happens at capillaries?
oxygen, nutrients, and carbon dioxide diffuse.
What is the most numerous type of vessel?
capillary
Types of Capillary
continuous, fenestrated, and discontinuous.
How to identify type of capillary
by location
Continuous Capillary
complete basement membrane. Complete endothelial cells joined by tight junctions. Allows gas transport. Found in muscle, brain, lung
Fenestrated Capillary
complete basement membrane. Holes in endothelial cells allow for substantial transport of fluid, ions, hormones, and nutrients. Found in intestine, glomeruli, endocrine glands
Discontinuous Capillary
incomplete basement membrane and endothelial cells. Large molecules and cells can pass through gaps. Liver (sinusoids), spleen (sinuses), lymph nodes (sinuses), bone marrow, placenta
Veins
low pressure vessels that take blood towards the heart
Types of Veins
venules, medium-sized veins, large veins
Venules
thin walled, lack a tunica media.
How to differentiate a venule from a capillary
by diameter
Medium-Sized Veins
thin muscular tunica media. Valves for one-way flow. More irregularly shaped than artery.
Large Veins
thin muscular tunica media. Valves to prevent blood from flowing back into capillaries.
What is the venous partner to the arteriole?
venule
What is the venous partner to the muscular artery?
medium-shaped vein
Intimal Bodies
small mineralizations of the intima of the submucosal intestinal vessels in horses. Significance is unknown
What is the endocardium made of?
simple squamous epithelium
Hemangiosarcoma
malignant tumor of endothelial cells that tends to occur in the right atrium of dogs
Valves
thin connective tissue core. Covered with endothelial/endocardial cells.
Myocardium
cardiac muscles- striated with central nuclei and branching myocytes. Purkinje fibers
Cardiac Skeleton
four fibrous rings. May be partly cartilagenous (cats) or osseus (cattle)
os cordis
heart bone in cattle
Epicardium
Has adipose tissue, coronary arteries, and is covered in mesothelium
How are flat mesothelial cells distinguished from endothelial cells?
by location
Pericardial Sac
thin collagen layer with mesothelium on both sides. may contain adipose tissue
Layers of the pericadrium
parietal layer and visceral layer.
Lymphatic Vessels
contain lymph fluid and lymphocytes
Characteristics of lymphatic vessels
thin-walled and have valves. Look similar to veins
Lymphatic Capillaries Direction of Flow
fluid flows toward heart only.
Components of Lymphatic Capillaries
discontinuous endothelial cells and basement membrane
Main function of lymphatic capillaries
constantly pick up fluid, protein, and cells from interstitium and return it to the circulatory system
What uses lymphatic vessels to metastasize?
carcinomas
Larger lymphatic vessels
pass through lymph nodes and empty lymph into large veins.
Largest lymphatic vessel
thoracic duct (left lymphatic duct)
