Session 8

Question 1

What are the different types of bone?

Answer 1

short
long
flat
irregular
sesamoid

Question 2

Describe the long bones

Answer 2

longer than they are wide
include the femur (the longest bone in body) and small bones in the fingers
long bones are mostly located in the appendicular skeleton

function: to support the weight of the body and facilitate movement

Question 3

Describe the short bones

Answer 3

approximately as long as they are wide
wrist and ankle joints
the carpals in the wrist (scaphoid) and the tarsals in the ankles (calcaneus)

part of the appendicular skeleton
function:
short bones provide stability and some movement

Question 4

Describe the flat bones

Answer 4

somewhat flattened, with roughly parallel opposite edges
in the skull (occipital), thoracic cage (sternum and ribs), pelvis (ilium)

function:
protects internal organs, also provide large areas of attachment for muscles

Question 5

Describe the irregular bones

Answer 5

vary in shape and structure and therefore do not fit into any other category
fairly complex shape
vertebrae and sacrum

function:
protect internal organs
vertebrae in the vertebral column protect the spinal chord
pelvis (sacrum) protect organs in the pelvic cavity
provide important anchor points for muscle groups

Question 6

Describe the sesamoid bones

Answer 6

bones embedded in tendons
small, round bones found in the tendons of hands, knees and feet
the patella (kneecaps) is an example of a sesamoid bone (generated postnatally)

functions:
protect tendons from stress and damage from repeated wear and tear

Question 7

What is cancellous and compact bone?

Answer 7

cancellous bone
forms a network of fine bony columns or plates to combine strength with lightness
the spaces are filled by bone marrow

compact bone
forms the external surfaces of bones and comprises approx 80% of the body’s skeletal mass

Question 8

What are the types of bone marrow?

Answer 8

red marrow
full of developing red blood cells
rich blood supply
only found in spongy bone
function: to. replenish cells in the blood
(haemopoiesis)

yellow marrow
full of adipocytes
poor blood supply
function: shock absorber and energy source, can convert to red marrow
(provides every for developing blood cells)

Question 9

Describe cancellous bone

Answer 9

each trabeculum consists of numerous osteocytes embedded within irregular lamellae
osteoblasts and osteoclasts on their surfaces act to remodel them

Question 10

How do the maturing cells leave the bone?

Answer 10

blood travels down the nutrient artery and up into the sinusoidal capillary bed
bone marrow cells enter the bloodstream through the sinusoidal capillaries and travel out in the blood through the central marrow vein and into t he vena comitans

Question 11

Which way are other cells released?

Answer 11

released through sinusoids

have an incomplete basement membrane

Question 12

Describe sinusoid vessels

Answer 12

Cells have aquaporins and glycophorins on their membranes (holds in the bone marrow)
These allow emerging cells to attach to the endothelial cells and escape

Question 13

Describe the circulation, involving RBCs and WBCs

Answer 13

Newly formed RBCs travel from
Venule ➡️ intermediate vein ➡️ larger vein➡️ vena cava
During circulation RBCs become mature (in 2 days)
Newly formed WBCs take the same route
- T cells need the actions of the thymus to become mature and lymphatic organs (waits here to be needed)
- B cells already mature

Question 14

Describe the microcirculation with capillaries

Answer 14

Flow in capillaries is controlled by precapillary sphincters
These PS are located between arterioles and capillaries
- contain SMC, contraction
- when open blood flows to capillary bed
- when closed no blood flows to capillary bed

Function: controls fluid exchange between the capillaries and the body tissues
Larger cells cannot pass through the capillaries and bypass the capillary bed

Question 15

How are veins structured?

Answer 15

Vein= an elastic blood vessel that transports blood from various regions of the body to the heart 
Consists of three layers:
Tunica intima, endothelial cells
Tunica media, elastic fibres and SMC
Tunic externa, elastic fibrous capsule

Non return fibroelastic cartilaginous valves assist flow towards the heart
Low pressure system so relies on muscle contraction to return blood to the heart
Vein problems occur due to either a blood clot or a vein defect behind the valves

Question 16

What are the different types of veins?

Answer 16

Pulmonary- carry oxygenated blood from the lungs to the atrium of the heart
Systemic- return oxygen depleted blood from the rest of the body to the right atrium of the heart
Superficial- located close to the surface of the skin and are not located near a corresponding artery
Deep veins- located deep between tissues and are typically located near a corresponding artery with the same name

Question 17

What is the size of veins?

Answer 17

Range in size from 1mm to 1-1.5cm in diameter

Smallest veins are venules (receive blood from arterioles and capillaries)
The venules branch into larger veins (eventually carry blood to the largest veins in the body, vena cavae)
The superior vena cava and inferior vena cava drain into the right atrium of the heart

Question 18

Describe the structure of arteries

Answer 18

Elastic blood vessels that convey blood away from the heart
Three layers
Tunica intima- elastic membrane lining and smooth non fenestrated endothelium
Tunica media- smooth muscle and elastic fibres, this layer is thicker in arteries than in veins and has two distinct elastic layers
Tunic externa/ adventia- strong outer covering composed of collagen and elastic fibres
(Allows arteries to stretch but prevents over expansion due to higher blood pressures than in the veins)
Smaller lumen diameter than veins

Question 19

Compare the arteries and veins

Answer 19

Walls of arteries are thicker to deal with the higher blood pressure

(In the h and e stain the vein has a funny shape as it has collapsed during processing as doesn’t have the strength of the artery

Question 20

Compare the functions of the arteries, veins and capillaries

Answer 20

Arteries
Carry blood away from the heart at high pressure
Narrow lumen
Strength and elasticity needed to withstand the pulsing of the blood, preventing bursting and maintain high pressure wave
Helps to maintain high blood pressure preventing blood flowing backwards

Capillaries
Supply all cells with them requirements
Take away waste products
Very narrow lumen
No need for strong walls as most of the blood pressure has been lost
Thin walls and narrow lumen bring blood into close contact with body tissue, allowing diffusion of materials between capillary and surrounding tissues

Veins
Return blood to the heart at low pressure
Wide lumen
No need for strong walls as most of the blood pressure has been lost
Wide lumen offers less resistance to blood flow

Question 21

What are collateral blood vessels?

Answer 21

these are usually arterioles that provide protection for tissues that may become compromised
provide an alternative path for arterial blood flow
some form due to chronic disease like ischaemia
some formed in development
take time to develop

Question 22

What is vasculogenesis and angiogenesis?

Answer 22

V
formation off new blood vessels
angioblast precursors (bone marrow)
eg during embryonic development, newly formed cancers and endometriosis (uterus lining develops somewhere else)
A
formation of new blood vessels from existing blood vessels
eg during fetal development, collateral arteries, postnatal lung development

Question 23

Describe vasculogenesis in the embryo

Answer 23

first step is formation of the single vessel
VEGF produced by the endoderm, generates the primary plexus which folds into a primary vessel

sprouting
FGF produced by mesenchymal cells, pericytes convert to SMC
slow, takes hours to days

intussusception
primary vessel forms twin vessel, multiple growth factors needed (this is why arteries and veins are so close together in neurovascular bundles)
quick, takes minutes to hours

Question 24

What is the pericyte?

Answer 24

immature smooth muscle cell
- found in the basal lamina close to the basement membrane
key component of capillaries
has contractile properties
also involved in nerve cell communication in the blood brain barrier
(can also differentiate to endothelial cell, SMC or fibroblast)

function:
prevents endothelial cell proliferation
maintains tight capillaries (in blood brain barrier for eg and in the retina)

Question 25

What are haemopoietic stem cells?

Answer 25

found in the bone marrow
large bank to fuel cells of the blood
haemopoietic stem cells have the ability to self replicate and differentiate further
common progenitors only have the ability to differentiate into lineage bound (lymphoid and myeloid progenitors)
constantly replicating and differentiating driven by multiple hormones and chemical messengers

Question 26

Describe the structure of RBCs

Answer 26

life span of 120 days after which are degraded by liver/ spleen
7 micrometers in diameter
biconcave shape to increase surface area for diffusion
no nucleus/ minimal organelles to maximise oxygen holding capabilities
no mitochondria to ensure oxygen not used by RBC
haemoglobin increase the affinity of oxygen binding (made from iron)

Question 27

What is erythropoiesis?

Answer 27

erythroblasts start off with large nucleus, prominent nucleoli and large amounts of RNA (therefore cytoplasm appears blue)
gradually nucleus shrinks and is removed along with majority of RNA

Question 28

What are reticulocytes?

Answer 28

the final step before a mature erythrocyte (once nucleus is removed)
only a small amount of RNA remains to help make haemoglobin
this is removed in 1-2 days
high amounts of reticulocytes can present in the blood when body is recovering from blood loss

Question 29

How does the body stimulate more red blood cell production?

Answer 29

the kidney senses tissue hypoxia (low oxygen)

the kidney increases secretion of erythropoietin

Question 30

What is erythropoietin?

Answer 30

a glycoprotein produced by the kidney to increase levels of RBC
acts to stop programmed cell death (apoptosis) of erythrocyte progenitors
made in liver during fetal life and is taken over by kidney after birth

Question 31

What are granulocytes?

Answer 31

sub group of WBC
fight infections/ inflammation
named due to presence of granules within cytoplasm
act to mediate inflammatory reactions in body
act by releasing cytokines, interleukins, leukotrienes, etc which recruit other immune cells

Question 32

Describe neutrophils

Answer 32

often first responder and first line of defence against bacteria
can kill bacteria in multiple ways 
multilobed nucleus 
3 types of granules 
most abundant of the granulocytes

granules contain lysosomes, MMPs and gelatinase
function of phagocytosis
acts as the middle person
functions involve neutrophil extracellular traps (NETS)- these are chromatin/ DNA nets the neutrophil sends out and captures bacteria
respiratory burst ( a neutrophil can make free radicals which damage DNA of bacteria and lead to apoptosis)

Question 33

What is G-CSF?

Answer 33

secreted by multiple immune cells in the body and endothelial cells

Question 34

Describe basophils

Answer 34

release histamine to trigger inflammation
mediate hypersensitivity reactions
bilobed nucleus
purple granules
granules contain histamine and heparin

Question 35

Describe eosinophils

Answer 35

phagocytose pathogens
fight parasitic worms and have a role in inflammation
2 nuclear lobers
spheric eosinophilic granules (acid loving)
granules contain:
anithelminthic proteins such as basic protein and eosinophil cationic protein
cell component destroying enzymes

Question 36

What is granulopoiesis?

Answer 36

all three lineages go through the process of:
nuclear condensation and lobulation
formation/ increased numbers of granules

Question 37

What are monocytes?

Answer 37

monocyte in blood, macrophage in tissue
first line of defence
phagocytose pathogens, cell dervish and senescent cells
present foreign antigens
largest of all mature blood cells (12-17micrometers)
unilobular ‘horseshoe’ shaped nucleus

Question 38

Describe thrombocytes

Answer 38

platelets
function to stop bleeding and mediate haemostasis
2-3micrometers
biconvex shape
no nucleus, just cytoplasm
contains vast amount of proteins and clotting factors
special receptors on surface causing platelet aggregation

Question 39

What is thrombopoiesis?

Answer 39

up regulated by thrombopoietin in liver

formed from a megakaryocytic breaking down which eventually forms 2000-3000 platelets

Question 40

Describe the two lymphocyte cells

Answer 40

B cells
main function revolves around production of antibodies
each B cell specific to a specific antigen
can activate t cells
play a part in humoral adaptive immunity
maturation occurs in bone marrow then in intestines, spleen, lymph nodes

T cells
kill virus infected cells, neoplastic cells and transplanted tissue
carry out cell mediated immunity
activate B cells to make antibodies using IL4
large nucleus with small rim of cytoplasm
proliferation and activation caused by IL2
microscopically indistinguishable from B cells

Question 41

How do T cells migrate?

Answer 41

start off in the bone marrow or fetal liver and then migrate to thymus and mature
then migrate to secondary lymphoid organs where they will wait until activation

Question 42

Describe plasma

Answer 42

makes up the majority of circulating volume
the supporting medium for all circulating blood vessels
92% water 8% protein ions
contains albumin, clotting factors, hormones, cytokines, antibodies etc