blood and blood vessels

Question 1

vascular system layers

Answer 1

tunica intima, tunica media, tunica adventitia

Question 2

tunica intima

Answer 2

inner layer, single layer of squamous epithelial cells (endothelial cells) supported by a basal lamina and thin layer of connective tissue

Question 3

tunica media

Answer 3

middle layer, made of predominately smooth muscle. Thickness varies tremendously.

Question 4

tunica adventitia

Answer 4

outer layer, made of supporting connective tissue

Question 5

elastic arteries

Answer 5

largest arteries, many sheets of elastic fibres in tunica media to provide elastic recoil. only inner part can obtain nutrients therefor vessels have own blood supply

Question 6

arterioles

Answer 6

as arteries become smaller they loose smooth muscle from TM until arterioles that have only 1/2 layers in TM. important in controlling blood flow in tissue

Question 7

capillaries

Answer 7

composed of endothelial cells and a basal lamina. 3 types

Question 8

3 types of capillaries

Answer 8

continuous, fenestrated, discontinuous

Question 9

continuous capillaries

Answer 9

muscle, nerves, lungs, skin

Question 10

fenestrated

Answer 10

have small pores, gut mucosa, endocrine glands, kidney

Question 11

discontinuous

Answer 11

have large gaps, liver, spleen, bone marrow

Question 12

microvasculature

Answer 12

small arteriole connected to a post capillary venule through network made of metarterioles, thoroughfare channels and capillaries. Precapillary sphincters made of smooth muscle at the beginning of the capillary help control flow through network

Question 13

venules

Answer 13

capillary networks drain into them. important site for exchange. once vessels begin to acquire smooth muscle in TM they’re venules

Question 14

veins

Answer 14

thin continuous TM and obvious TA. large veins have thick TA which incorporates bundles of smooth muscle. have valves to prevent backflow

Question 15

lymph vascular system

Answer 15

system of thin walled vessels that drain excess tissue fluid into blood stream. transports lymph to lymph nodes for immunological surveillance. no central pump, smooth muscle in walls, pressure in tissue and compression of vessel produces flow

Question 16

components of blood

Answer 16

erythrocytes, leukocytes

Question 17

erythrocytes

Answer 17

red blood cells, mature cells dont have a nucleus. 1/3 volume taken up by haemaglobin. flexible cytoskeleton allows them to fit in small gaps. last 4 months, old cells removed by spleen and liver

Question 18

leukocytes

Answer 18

white blood cells. proportion = neutrophils, lymphocytes, eosinophils, monocytes and basophils

Question 19

neutrocytes

Answer 19

most common white blood cell. stain badly as theyre neutral circulate in inactive state but if stimulated they can enter tissue as highly mobile phagocytes. short lived, high % of bone marrow is devoted to their production

Question 20

eosinophils

Answer 20

have bilobed nucleus, important in inducing and maintaining inflammation. important in fighting parasitic infection. high affinity for acidic dye, circulate for 8-12 hours. larger than neutrophils

Question 21

basophils

Answer 21

rarest granulocytes affinity for basic dye, bilobed nucleus. granules contain histamine, heparin and other inflammatory mediators. they act as receptor cells in allergic reactions. if triggered they’ll release their granules

Question 22

monocytes

Answer 22

serve as the precursors of tissue macrophages and together they form what is termed the mononuclear phagocyte system. Widely distributed, particularly found on loose connective tissue. Have numerous small lysosomal granules in cytoplasm. Largest cell, non-lobulated nucleus.

Question 23

lymphocytes

Answer 23

round nucleus surrounded by thin rim of cytoplasm no visible granules. 2 classes B cells and T cells. Both types of lymphocytes arise in the bone marrow, but T cells differentiate in the thymus. Both cell types participate in the specific immune response. B cells give rise to antibody secreting plasma cells while T cells form a complex set of cells that perform many defence functions.

Question 24

platelets

Answer 24

included in formation of blood. key role in homeostasis. well developed cytoskeleton which participate in extrusion of granules and in clot retraction. has some organelles but no nucleus. have some coagulation factors

Question 25

hemopoiesis

Answer 25

formation of blood

Question 26

blood formation during gestation

Answer 26

- Earliest site for erythrocyte formation is outside the embryo in the yolk sac beginning at about 3 weeks gestation. Later, the liver and to some extent the spleen is colonized by hemopoietic stem cells. Thus during the second trimester the liver is the principal site of blood formation.

Question 27

blood formation after birth

Answer 27

- By birth the bone marrow is main site as bones enlarge there is excess capacity so many bones stop production. By skeletal maturity only vertebrae, ribs, skull, pelvis and proximal femurs retain ability. In emergency the other bones can start production again

Question 28

megakaryocytes

Answer 28

hematopoirtic cells

Question 29

what do they do

Answer 29

- Megakaryocytes are large cells of bone marrow that produces platelets. It undergoes multiple duplications of its nuclear material but doesn’t undergo nuclear or cell division – so the nucleus is very large. The platelets are formed as extensions at the outer margin of the cell which fragment from the cell.