Histology and Blood Vessels Flashcards by Lindsay Garrick

What components make up blood?

Plasma (55%)
Red cells (erythrocytes)
White cells (leukocytes)
Platelets

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What is in the blood plasma?

Water (90%)
Proteins
Nutrients
Salts

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What are erythrocytes?

Red blood cells

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What are leukocytes?

Name 5

White blood cells

neutrophils
eosinophils
basophils
lymphocytes
monocytes

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What are platelets?

Cell fragments, 2 micrometers, involved in hemostasis
Well developed cytoskeleton which aids extrusion of granules and the clotting
Some organelles, no nucleus
Contain coagulation factors within some granules

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What is the internal elastic membrane?

Layer of elastic tissue separating tunica intima and tunica media

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What is the external elastic membrane?

Layer of elastic tissue separating tunica media from tunica adventitia

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Do elastic fibres show up with common stains?

No, specialised stains must be used

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What are elastic arteries?

Large arteries which contain less smooth muscle and more elastic fibres within tunica media to enable them to stretch and shrink during the cardiac cycle and maintain consistent blood pressure

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What is the vaso vasorum?

Blood supply to tissues within large blood vessel wall (excluding tunica intima)

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Why do tissues in the large blood vessel walls need a separate blood supply?

Only tunica intima can access nutrients and oxygen from blood in lumen

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How is the vessel wall of a small arteriole different to that of an artery?

Less smooth muscle

Very small tunica adventitia

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What are vaso nervorum?

Nerves supply blood vessels

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Describe the structure of a capillary

No smooth muscle
Simple squamous epithelial cells connected to basal lamina
Diameter of 4 - 8 micrometers (RBC is 7 micrometers)

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Name the three types of capillary

Continuous
Fenestrated - contain small pores
Discontinuous / sinusoidal - contain large gaps between cells

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At what point does capillary turn into a venule?

When patches of smooth muscle start to appear in the tunica media

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Where do capillaries drain to?

Post - capillary venules consisting of endothelial cells and thin layer of connective tissue

Important site for exchange eg cells from blood can move into tissues during inflamation response

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Describe structure of veins

Contain valves to prevent backflow of blood
Thin tunica media with a layers of few smooth muscle cells
Substantial tunica adventitia

Largest veins have very large tunica adventitia with bundles of longitudinal smooth muscle

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Do lymph vessels contain valves?

Yes

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Where do lymphatic vessels take lymph?

To nodes for immune surveillance

Back to blood stream at veins at root of neck

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How is lymph moved through the lymphatic system?

Via

smooth muscle in vessel walls
hydrostatic pressure in tissue
compression of vessels by voluntary muscles
valves

How is lymph moved through the lymphatic system?

Via

smooth muscle in vessel walls
hydrostatic pressure in tissue
compression of vessels by voluntary muscles
valves

How much blood does the average adult have?

4.5 - 6 litres

What is serum?

substance in blood obtained by the centrifugation of blood from which the clotting factors have been removed

What happens to the components of blood if spun in a centrifuge?

Plasma/serum found at top White cells next Red blood cells at bottom

What happens to an erythrocyte after 4 months?

Removed from circulation by spleen and liver

What is a neutrophil and what is it's function?

Type of granulocyte - contains many granules which are difficult to stain with either basic or acidic dyes Most common leukocyte Multi-lobed nucleus Inactive in circulation, activated by presence of pathogen/inflammation, they move into tissue and act as highly motile phagocytes Short-lived, production in bone marrow high

Describe eosinophils

Granulocytes with affinity for red acidic dye eosin Bilobed nucleus Slightly larger than neutrophils

Describe the function of esosinophils

Released from marrow and circulate for 8-12 hours, then move into tissue (especially spleen, lymph nodes, and GI tract) and live there Their granules contain hydrolytic enzymes Important in initiation and maintenance of inflammation (allergic reaction, asthma) and fighting parasitic infection

Describe basophils

Rarest of granulocytes High affinity for basic dyes such as methylene blue, stains them purple/blue Bilobed nucleus, often obscured by granules Granules contain heparin, histamine, and other inflammatory mediators

What do basophils do?

They are Effector cells during allergic reactions When a specific allergen binds to their IgE receptors, the granules are released (degranulation) Leads to allergic reaction eg hayfever, allergic asthma, allergic dermatitis

What is the mononuclear phagocyte system?

monocytes and macrophages

Where are macrophages found?

Everywhere but especially in loose connective tissue

Describe a monocyte

Is an agranulocyte, contain many small lysosomal granules

Describe a monocyte

Is an agranulocyte, contain many small lysosomal granules Largest blood cell Non-lobulated nucleus, nucleus kidney-bean shape

Name three members of the mononuclear phagocytic system which do not move around the body

Kupffer cells in liver Microglia in brain Langerhan's cells in skin

Do lymphocytes contain granules?

No, they are agranulocytes

Describe the nucleus of a lymphocyte

Round

What do B and T cells have in common?

Appear identical in normal staining, no granules, arise in bone marrow, involved in specific immune response T cells differentiate in thymus

What is the function of a B cell?

Produce antibody secreting plasma cells

What is the function of a T cell?

Defending against infection Inducing apoptosis Aiding other immune cells

When are the first erythrocytes made?

At 3 weeks (within womb) in yolk sac

What is hemopoiesis?

the production of blood cells

During the 2nd trimester, where is most of the blood formed?

Liver Some hemopoeitic cells in spleen

After birth, where is the main site of blood production?

Bone marrow Baby - all bones Adult - Full (Femur) Sleepy (skull) Hippos (hip) Happily (humerus) Rest (rib) Very (vertebrae) Still (sternum) Marrow in other bones contains adipose cells but can making blood if necessary

What are megakaryocytes?

Very large cells (30 to 100 micrometers) which produce platelets in bone marrow Duplicates nuclear material but never divides nucleus/cell - nucleus is huge Platelets are fragments separated from periphery of cell

Where are continuous capillaries found?

muscle, nerves, lungs, and skin

Where are fenestrated capillaries found?

gut mucosa, endocrine glands, and kidneys

Where are discontinuous/sinusoidal capillaries found?

liver, spleen, and bone marrow

Describe the structure of an erythrocyte

Biconcave discs, no nucleus and no organelles, 33.3% of volume is haemoglobin

How big is an erythrocyte?

7 micrometers

Why can an erythrocyte squeeze through a gap smaller than itself?

Flexible cytoskeleton