Lecture 7 - Vascular Disorders and Thrombosis

what is the thymus organ?

The thymus is a lymphoid organ located in the upper chest, responsible for the maturation of T-cells, which are crucial for the adaptive immune system. It plays a key role in the development of immune responses.

is this thymus normal?

yes

is this normal thymus?

no

what are the major parts of the circulatory system?

• heart

• arteries/veins

• lymphatics

which direction do arteries send blood?

carry blood away from the heart to the body; extreme vascular resistance and increased pressure

which direction do veins carry blood?

from body towards heart, low pressure

whats the micro-anatomy of the vessels?

Aorta > Arteries > Arterioles > Capillaries < Venules < Veins < Vena Cava

Characteristics of arteries?

• large lumen: minimal resistance

• Thick vessel walls: smooth muscle / elastic fibers

characteristics of arterioles?

• narrow lumen

• respond to sympathetic and parasympathetic innervation (constriction and relaxation of vessels)

what are the 3 layers in the endothelium in the vessels?

• tunica intima

• tunica media

• tunica adventitia

what is the tunica intima - arteries

• endothelium

• basement membrane

• internal elastic lamina

what is the tunica media - arteries?

• smooth muscle

• collagen, reticular, and elastin fibers

• external elastic fibers

what is the tunica adventitia - arteries?

• connective tissue

• vasa vasorum (microvessels)

• lymphatic vessels

• nerve fibers

what is the function of the capillaries?

site of nutrient and waste exchange

what are the three types of capillaries?

• continuous

• fenestrated

• discontinuous

Continuous capillaries characteristics?

• uninterrupted endothelial cell layer, allowing for selective transport.

• They are primarily found in muscle, lungs, and central nervous system.

• BRAIN important - whole reason for blood brain barrier

• They have tight junctions and minimal intercellular clefts.

Fenestrated capillaries characteristics?

• Endothelial cells with pores (fenestrae), facilitating greater permeability to larger molecules.

• Found in areas requiring extensive exchange, such as renal glomeruli, intestinal villi, endocrine glands, choroid plexuses, and ciliary processes of the eye

Discontinuous capillaries characteristics?

• Large gaps between endothelial cells, allowing for free exchange of larger molecules and even cells.

• Commonly found in the liver, spleen, bone marrow and lymph nodes

• immune surveillance and detoxifying blood

characteristics of veins/venuoles?

• mostly collagen (distention > contraction)

  • little smooth muscle and elastin

  • can hold up to 65% of total blood volume

• Blood passage depends on:

  • valves to prevent backflow

  • contraction of skeletal muscles

tunica intima - veins?

• endothelium

• basement membrane

tunica media - veins?

• smooth muscle

• collagen, reticular, and elastin fibers

• predominantly collagen and less smooth muscle

tunica adventitia - veins?

• modest connective tissue

• vasa vasorum (microvessels)

• occasional nerve fibers

why is elastin stain important?

Microanatomy:

• tunica intima (endothelium, elastin)

• tunica media (smooth muscle)

• Tunica adventitia (connective tissue)

Elastin gives elasticity to vessels

what are lymphatics?

• surround microcirculation

• begin as blind ended lymphatic capillaries

• overlapping endothelial cells and large interendothelial gaps (can accommodate larger particles)

• valves and contraction of skeletal muscles to move lymph forward towards heart

what is found in lymphatics?

• lymph

• lipids

• ECF

• inflammatory cells

endothelium?

• single layer of endothelial cells lines all components of the circulatory system

endothelium function?

• fluid distribution

• inflammation

• immunity

• angiogenesis

• hemostasis

what is Rete Mirabile?

specialized vascular networks formed by arterial blood vessels through the center of large venous sinuses

what is the function of Rete Mirabile?

countercurrent exchange

• regulating temperature

• ionic contraction gradients

• O2/CO2 exchange

• equalizes blood pressure

what is the interstitium?

• extravascular compartment

• space between parenchymal and stromal cells and microcirculation

Functions of Interstitium?

• provides pathways used by the microvasculature (vascular adventitia), lymphatic vessels, nerves and trafficking leukocytes

• module systemic physiologic properties exerted by parenchymal cells

• General fluid pool/reservoir providing cushioning effects for organs, water/ion reserves

• structural framework for cell survival

what is the extracellular matrix?

the structural, adhesive, and absorptive components within the interstitium

what is the extracellular matrix composed of?

• type 1 collagen (mainly)

• glycoproteins

• glycosaminoglycans

• proteoglycans