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Words

adipose, adventitia, arteriole, artery, blood, bundle, capillary, capsule, cell, circular, collagen, compact, connective, continuous, cross, distribute, elastic, elastic, endothelium, erythrocyte, fenestrated, fiber, fine, flap, ganglion, hilus, inner, internal, interspersed, intima, laminae, large, layer, longitudinal, loose, lumen, lymph, lymphatic, media, medium, membrane, muscle, muscular, narrow, nerve, node, oblique, pericyte, perineurium, red blood cell, sinusoid, small, smooth, sphincter, sub-endothelium, sympathetic, terminal, thick, thin, tissue, transverse, tunica, unmyelinated, valve, vasa vasorum, vasomotor, vein, venule, vessel, wall

Cells

erythrocyte

fat cell

nerve cell

pericyte

red blood cell

smooth muscle fiber

squamous cell

Tissues

adipose tissue

collagen fibres

elastic fibres

loose connective tissue

subendothelial connective tissue

Structures

arteriole, artery, capillary, capsule, continuous capillary, elastic laminae, endothelium, fenestrated capillary, internal elastic membrane, large vein, lumen, lymph node, lymph vessel, medium vein, muscular artery, nerve, nerve fiber, neurovascular bundle, perineurium, precapillary sphincter, sinusoidal capillary, sympathetic ganglion, tunica adventitia, tunica intima, tunica media, valve, vasa vasorum, vein, venule

Slides: Vessels

• Muscular artery and vein: Slide 69
• Muscular artery and vein: Slide 70
• Elastic artery: Slide 67
• Elastic artery: Slide 49
• Large vein: Slide 92
• Large vein: Slide 109
• Ductus thoracicus: Slide 75
• Ductus thoracicus: Slide 65

Slides: Accessory structure

• Semilunar valves in the blood vessels of cardiac muscle: Slide 47

Slides: Cardiac muscle

• Heart muscle (longitudinal section): Slide 20
• Heart muscle (cross section): Slide 77
• Heart muscle: Slide 86

Question to ponder

• What would happen if ALL capillaries were filled with blood?
• How does “stuff”* get into and out of blood?
• *Stuff = gasses, nutrients, cells, molecules
• How does the type of epithelium in arteries, capillaries, veins and lymph vessels differ?
• Where does atherosclerosis happen?
• Where does aneurysms happen?

Objective

• Compare and contrast the three tunics
• Distinguish between:
• Elastic arteries and muscular arteries
• Arteries and veins
• Identify capillaries
• Identify lymphatic vessels
• Identify nerves
• Identify small associated features
• Describe the functioning of the capillary bed
• Describe portal systems
• Describe end-arteries

Cardiovascular system

• O2 and nutrients are distributed by blood which the heart pumps through the blood vessels
• Lymphatic system collects surplus tissue fluid as lymph

Cardiovascular System 1/2

• Heart
• Combined 2 sided pump
• Cardiac muscle fibers
• Elastic arteries
• Receive blood under pressure from heart
• Elastic fibers
• Muscular arteries
• Distribute blood
• Smooth muscle
• Arterioles
• Reduce pressure
• Artery with narrow lumen

Cardiovascular System 2/2

• Capillaries
• Facilitate interchange
• Thin walls
• Metarterioles
• Rapid bypass of capillaries
• Blood pressure regulation
• Venules
• Looks like wide capillaries
• During acute inflammation produce plasma and leucocyte exudate
• Veins
• Return blood to heart

General organisation

• Three concentric coats (tunics)
• Tunica intima
• Tunica media
• Tunica adventitia

Tunica intima

• Blood vessels
• Lining membrane = endothelium
• Underlying basement membrane (BM)
• Variable amount subendothelial connective tissue (CT)
• Internal elastic lamina
• Absent some small vessels
• Heart
• Tunica intima = endocardium
• Endothelium and CT

Tunica media

• Blood vessels
• Two components as concentric layers
• Smooth muscle fibers
• Elastic fibers
• Absent in smaller vessels
• Heart
• Highly developed muscle layer
• Myocardium

Tunica adventitia

• Blood vessels
• Loose CT
• Some smooth muscle cells
• Own blood vessels
• Vasa vasorum
• Heart
• Epicardium
• CT + mesothelium

Heart 1/2

• Endocardium = tunica intima
• Endothelium
• BM
• Loose CT
• Dense CT
• Fat cells
• Branches of impulse conducting system
• Merge with endomysium of myocardium
• Myocardium = tunica media
• Cardiac muscle fibers
• Endomysial loose CT
• Contains capillaries and lymphatics
• Epicardium
• Fibroelastic CT
• Blood vessels, lymphatics, Nerve fibers, fat tissue
• Blends with endomysium
• Mesothelium
• Squamous epithelial cells
• Pericardial cavity

Heart 2/2

• Pericardial cavity
• Pericardium
• Serous pericardium
• Mesothelial serous lining
• Fibrous pericardium
• Fibro-elastic external layer

Valves

• Flap of intima
• Core
  • Irregular dense CT
  • Without blood vessels
  • Some elastic fibres
• Covered with endothelium

Muscular artery

• Intima
• Thin
• Endothelium
• BM
• Thin subendothelial layer
• Internal elastic lamina
• Conspicuous wavy pink layer
• Media
• Thick
• Layers concentric smooth muscle
• Interspersed with some elastic fibers
• External elastic lamina
• Less conspicuous fenestrated layer elastin
• Adventitia
• Thickness vary but close to tunica media
• Elastic fibres with some collagen
• Contains vasa vasorum and lymphatics

Elastic artery

• Intima
• Thick = ¼ of wall of aorta
• Pale staining
• Endothelium
• Fenestrated elastic laminae mixed with elastic fibres
• Smooth muscle fibres and some fibroblasts
• Internal elastic lamina = first elastic lamina
• Media
• Thick
• Fenestrated elastic laminae ↑ with age
• Between laminae smooth muscle fibres that produce matrix
• Outer part supplied by vasa vasorum
• Inner part diffusion from lumen
• Indistinct external elastic lamina
• Adventitia
• Thin
• Elastic and collagen fibres
• Lymphatic capillaries and vasa vasorum

Arterioles

• Diameter < 100µm
• Wall thick relative to lumen (vs venule)
• Intima
• Endothelium
• BM
• Apposed internal elastic lamina
• Media
• One/Two layers smooth muscle
• Inconspicuous external elastic lamina
• Adventitia
• Few elastic and collagen fibres

Capillaries

• Small thin walled diameter 8 – 10µm
• Slightly wider than red blood cells
• Intima
• Lined with endothelium
• Resting on BM
• Lateral margins connected with tight junctions
• Do not extend around entire perimeter
• Slit-like intercellular clefts
• Tissue fluid and small molecules can pass through
• Brain: entire perimeter = blood-brain barrier with astrocytes
• Scattered pericytes
• Involved with blood-vessel growth
• Endo+BM+Pericytes = tunica intima
• No Media
• Adventitia with little CT

Capillaries

• Three types
• Continuous
• Most parts
• Endothelium uninterrupted
• Allow passage water and ions and small molecules
• Fenestrated
• Circular fenestrations (windows) in cytoplasm
• More permeable varies according to location
• Larger molecules
• Small intestine, kidneys, endocrine organs
• Sinusoids
• Thin-walled with wide lumen
• Associated population of macrophages
• Extensive intercellular gaps
• Incomplete BM
• Large molecules can pass
• Plasma proteins and cells
• Bone marrow, liver, spleen, lymph nodes, endocrine organs

Metarterioles

• Looks like wide capillaries
• Structure
• Endothelium
• Discontinuous layer smooth muscle cells
• Connect arteriole direct to venule
• At origin of capillary is pre-capillary sphincter
• Constrict – channel blood past capillary bed

Venules

• Slightly wider
• Thin walled
• Receive capillaries and metarterioles
• Acute inflammation
• Leak plasma and leucocytes

Veins

• Thin walled
• Wide lumen
• Flattened in sections
• Internal and external elastic laminae inconspicuous
• Small, medium and large are similar

Small and medium Veins

• Intima
• Thin
• Endothelium
• BM
• Trace CT
• Meager internal elastic lamina
• Sometimes valves
• Media
• Few circular layers smooth muscle
• Exception = veins of limbs and below heart
• Thick
• Resist distension from gravity
• Adventitia
• Thickest
• Collagen and elastic fibres
• Fibroblasts
• Smooth muscle cells

Large Veins

• Intima
• Thin
• Endothelium
• BM
• Trace CT
• Meager internal elastic lamina
• Sometimes valves
• Media
• Poorly developed layers circular smooth muscle
• Adventitia
• Wide bundles longitudinal bundles smooth muscle in larger veins example vena cava inferior

Lymphatic System

• Collects excess tissue fluid
• Filters through lymph nodes
• Return to blood
• Start as blind-ending vessels

Lymphatic Capillaries

• Lined with endothelium
• BM incomplete or absent
• Allows macromolecules to enter
• No associated pericytes
• Wider than blood capillaries
• Collagen anchors in surrounding tissue
• Keep vessels open with oedema

Lymphatic Vessels

• No blood cells in lumen
• Similar to small and medium veins
• Endothelium
• Thin external coat of loose CT
• Medium and large lymphatics 3 coats
• Difficult to distinguish layers
• Intima
• Endothelium and elastic fibres
• Media and Adventitia
• Smooth muscle cells and CT fibres

Muscular artery & Vein

Slides 69 & 70

Majority

Macroscopic anatomy

• Holds true at the microscopic level
• Blood vessels in sheath
• Artery + Vein + Nerve + Lymphatics
• Example femoral sheath

Elastic artery

Slides 67 & 49

Aorta

Large Vein

Slides 92 & 109

Ductus thoracicus

Slides 65 & 75

What are end arteries?

End arteries

• Normal histology
• Pathology – necrosis
• Symptom – chest pain
• Diagnosis – Myocardial infarct
• What happened – heart attack

End arteries

• Heart
• Brain
• Eye
• Kidney

End artery

• Heart - Heart attack
• Brain - Stroke
• Eye - Blindness
• Kidney - Kidney attack failure

Portal System

Begin and Ends

In capillaries

Portal system

• Hepatic portal system
• Hypophyseal portal system

The End

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