Module 2 Topic 1: blood and Blood vessels

What is blood and what are its basic components

Blood is fluid connective tissue made up of amorphous ground tissue and cells that is pumped through the body using pressure differences in vessels and the heart.

Blood physical and chemical characteristics

• contibutes the about 8% of body weigth

• 4-5L in females and 5-6L in males

• pH of 7.35 -7.45 (alkaline - slightly basic)

• temperature of 37-38 with 0.5 differentiation

Blood -functions

• Regulation of temperature (dilation or constriction of vessels), pH ( controlled by concentration of ions in blood), water balance

• Protcetion: allows for the transportation of immune cells or clotting to prevnt blood loss)

• Transportation: moves hormones, oxygen CO2, nutrients and waste through the body)

when centrifuged what is found in layer 1 of blood

consists of the least dense components of blood that make up 55% of blood - contains plasma with includes water, nutrients, ions, waste and gases

when centrifuged what is found in layer 2 of blood

consists of the middle density components of blood that only make up 1% of the blood - contains platelets and white blood cells such as Neutrophils, Lymphocytes, Monocytes, Eosinophils, and basophils

when centrifuged what is found in layer 3 of blood

consists of the most dense components that make up 45% of blood - contains Red blood cells

Erythrocytes - features + aim

also known as Red blood cells that make up 99% of cells in the blood and transport watse and oxygen between heart and tissue

• biconcave disc shape used for oxygen transportation

• 7-8 micrometres in diameter

• no nuclei or organelles

• cytosol contains a lot of haemoglobin

what is haemoglobin + what its made of

Large protein in RBCs made up of multipolypeptides and iron

• formed in immature red blood cells that stil have organelles and nuceli

• made of 4 polypetides called globin which is bound to a pigment called heme that has an iron core

How are oxygen and CO₂ transported by blood

1 O₂ molecule binds to one of the haemoglobin molecules in a red blood cell, which contains about 300 million Haemoglobin molecules

CO₂ can either bind to the amino acids in haemoglobin or diffuse into plasma and transported as bicarbonate ions

Neutrophils

Most abundant ell type that is responsible for fighting bacterial infections

• blob inside is shaped like a uterus

lymphotcytes

out B and T cells that are used for immune responses

• blob is circle shaped

Monocytes

Float around the blood during transportation as monocytes but become macrophages when they enter injured tissue

• engulf foreign body objects, damaged cells and organelles and destroy them

• is the antigen presentation of lymphocytes

• bean like blob and wiggle outside layer

Eosinophils

found in very low concentration and fights parasitic infections or used in allergen responses

• bean like blob with lots of dots

Basiphils

not very prominent but used in allergy responses by secreting anticoagulants and histamines

what are platelets

disc-shaped fragments of a larger Megakaryocytic that are not cells

• 1 megakaryocytic = 4-2 micrometre diameter platelets

function of platelets

used to clot blood in order to prevent blood loss

• is a vasoconstrictor

• contains clotting factors and chemical attractants that elicits a response to ensure wound healing

• come together to form platelet plug

what is plasma

made up of 91% water and solutes including ions, proteins, gases, nutrints, waste and regulatory substances

• when the blood isn’t clotted plasma is serum

What is Haemopoiesis

the formation of components in the blood, such as RBCs, WBCs and platelets

• occurs in red bone marrow, which is a spongey, soft and hollow part of the bone

• uses stem cells

what can stem cells differentiate into and what can those products be made into

stem cells differntiate into either Myeloid progenitor cells ( can further differtiate into Erythrocytes, Leukocytes or platelets) or Lymphoid progenitor cells ( differentiates into T cells, B cells and natural killer cells)

Erythropoiesis + triggers

The formation of RBCs and platelets from Myeloid cells that is trigger by hypoxia or low oxygen levels

Erythropoiesis step 1

the kidney secretes the Hormone erythroproteins (ECP) which stimulates the differentiation of myeloid cells)

• uses endocrine signalling by secreting hormones out of endocrine glands or tissue and into the bloodstream to target cells

Erythropoiesis step 2

Myeloid cells differentiate into erythroblasts, which begin to synthesise haemoglobin

• erythroblasts can then differ in size, amount of haemoglobin and appearance of its nucleus

erythroblasts differentiate is various stages

• 1st they develop structures and features of RBCs

• make haemoglobin

• lose nucleus before being released into the bloodstream

Erythropoiesis step 3

Maturation of red blood cells ouccurs in blood stream over 1-2 days

• lose their organelles

RBCs life span + disposal instructions

Erythropoiesis occurs of 7 days, producing RBCs that last 120 days, meaning they require continuous turnover to maintain proper function

• when dead, they are broken down by macrophages

Leukopoiesis process

The production of WBCs is stimulated by growth factors and cytokines that cause the differentiation of myeloid cells in bone marrow

• mature inside th bone marrow or lymph tissue

Leukopoiesis life span

life span can vary depending of type with Neutrophills lasting hours - days and lymphocytes lasting weeks- years

What is Haemostasis and the phases it occurs in

The process at which blood clots to prevent blood loss and promotes wound healing occurs in three phases

• vascular phase

• platelet phase

• coagulation phase

Haemostasis: vascular phase

occurs due to vessel injury

• Vasoconstriction causes vascular spasms in the smooth muscle that reduce blood flow by drawing the vessel walls in on themselves ( less blood can get through vessel due to smaller lumen)

• endothelial cells, smooth muscle cells and fibroblasts divide for repair

• the endothelial plasma membrane becomes sticky to make its easier for platelets and other cells to attach to damaged vessel

Haemostasis: platelet phase

Platelets begin to adhere to site of injury and form a plug that initiates blood clotting

• buys body time for more permanent repairs

Haemostasis: coagulation phase

formation of blood clotts made of a mesh of robust fibrin

• fibrin = insouble protein

• adheres to existing plug

How does coagulation occur

1. clotting factors arerealeased in vascular and platelet phase

2. prothrombin in blood is converted to thrombin in pahse 1 and 2

3. throbin find fribrogen and converts it into fibrin which also floats in the blood until activation ( occurs in phase 2 and 3)

How are clots removed

when healing is almost finished the clot will retract and pull away from the edge of the vessel before dissolving in a process called fibrinolysis

what determines blood type

the presence / absence of specific antigens on the surface of the RBC

what is an antigennand its relation to immune system

glycoproteins on the outside of the cell that the immune system uses to detect what is self and what is not self

• plasma in blood has antibodies that determine what is self based on antigens

what are the blood types + relation to anti bodies

your antibodies are used to detect the presence of foreign antigens, which means that if you have

• A blood type with A antigens, then you have anti-B antibodies

• B blood type with B antigen, then you have Anti-A antibodies

• AB blood type with A and B antigen, then you have no antibodies (universal receiver)

• O blood type than you have no antigen, but both anti-B and anti-A antigens ( universal donner)

what are Rhesus proteisn

determine whether you have + or - blood

• if you have no Rh = -

• If you have Rh = + (most common)

what happens if you a transfused the wrong blood type

RBCs clump together and rupture, causing

• fever/chills

• kidney failure

• shock

• hypotension ( low BP)

• respiratory failure

• death

Blood vessels

The pathways at which blood travels around the body in a cycle

• arteries, arterioles, capillaries, capillary beds, venuloes, veins

pulmonary vs systemic circut

Pulmonary circuit: blood is being pumped from the heart to the lungs to oxygenate blood that has come back from the body

• a low-pressure system, as the blood does not have to travel very far

Systemic circuit: blood is pumped from the heart to the tissues to deliver oxygenated blood and bring back CO2

• higher pressure system as blood has to travel all over the body

Tunica intima composistion

the innermost layer of the blood vessel that is in direct contact with the blood and is made up of three layers

• Inner layer: endothelium of simple squamous cells ( allows for easy gas exchange) that are smooth to reduce friction

• Middle layer: sub endothelial CT to provide structure to the endothelium and integrity to the vessel wall

• outer layer: Internal elastic membrane (lamina) to provide structure and allow the vessel to stretch with blood flow (permeant for exchange between layers)

Tunica media composition

The middle + thickest layer of the vessel wall that is arranged in a circle around the vessel

• smooth muscle to regulate lumen diameter through constriction or dilation, causing changes in blood flow and pressure ( include collagen and elastic fibres)

• external elastic lamina that expands and recoils, and blood moves through to propel blood (not through arterioles or veins)

Tunica adventitia (externa) composition

outermost layer is made up of connective tissue with collagen and elastic fibres

• elastic bands scattered throughout smooth muscles

• protects and supports vessels

• prevents over extension

Arteries definition + types

Vessel that brings blood away from the heart and has thick walls to withstand a higher pressure of blood

• elastic arteries, Muscular arteries and arterioles

Elastic arteries: Location + structure

found closest to the heart and have the thickest walls at 10mm that allow for the expansion and recoil as blood is pumped through them

• helps maintain pressure gradient and is highly resistant

• Example: Aorta, Pulmonary artery, common carotid

Muscular arteries: Location + structure

Found further from the heart and undergoes less pressure, so elastocity is less important and has a diameter of 0.1 to 10 nm

• contains lots of smooth muscle fibres (more than elastic) consists of ¾ of the wall in 25 to 40 layers

Muscular arteries: function

More smooth muscle allows for greater constriction and dilation to adjust the rate of blood flow

• directs blood to organs or the musculoskeletal system, depending on demand

Arterioles: location + strcture

smallest arteries that lead into the capillary bed and have a thick wall relative to the lumen with a diameter of <5nm

• all layers are the same as other arteries but thinner

• endothelial lining is intact

Arterioles: function

Slows and resists the flow of blood via constriction and dilation

• reduces flow to prevent all the blood from filling the capillaries

• Muscle fibres tend to be slightly constricted to maintain vascular tone (dictates how much blood can flow to the tissues)

Artery - tunica composition

Elastic arteries: elastic fibre in every layer

• tunica advetura = thin

• Tunica media = thickest

• Tunica intima = 2nd thickest and endothelium ribbed for stretch

Muscular arteries: ¾ muscle

• TA: 2nd thickest

• TM: thickest

• TI: thinnest

Arterioles: no elastic membranes in TM and TI

• TA = very thin

• TM = thickest, 1-2 layers of muscle

• TI = 2nd thickest

Capillary Function + location

found in high concentration in areas of high metabolic activity such as muscle, liver, kidney, brain, and form capillary bed for exchange

• is the exchange site of nutrients, gases, and waste products (CO₂) between vessels and tissue( from interstitia fluid)

Capillary structure + types

Microscopic vessels with a diameter of 5-10 containing a single layer of simple squamous epithelium with a basement layer

• only just big enough for RBCs to pass through (microcirculation)

• walls must be leaky to allow substances through

• Includes continuous, femestrated and sinusoidal capillaries

Continuous capillary

The most common form of capillary that is found is all vascularised tissue

• has a complete endothelial lining held by tight junctions

• tight junctions are incomplete, leaving gaps (clefts for exchange

• allows through metabolic products like water, glucose, gases, and hormones

fenestrated capillary

found in the small intestine for nutrient absorption f kidneys for blood filtration

• has endothelial cells and tight junctions

• Plasma membrane contains pore that make it permeable to larger molecules (fenestrations)

• No. of fenestrations depends on location

Sinusoidal Capillary characteristic + location

found in the liver, spleen, bone marrow, lymph nodes and endocrine glands

• least common type of capillary

• has lots of large fenestrations

• incomplete plasma membrane

sinusoidal capillary function

Allow for the passage of large molecules such as plasma proteins or cells

• essential for organ function as they allow cells made by bone marrow to travel to necessary areas

Capillary Tunica Composition

TI

• has a single layer of endothelium with a basment membrane

• no elastic membrane

TM = none

TA= none

how are capillaires connected

Capillaries are connected via capillary beds, which connect arterioles and venuoles

• contains a web of capillaries that are interconnected and used to increase the surface area for exchange

• 1 capillary bed contains 10-100 capillaries

metarterioles definition

arterioles that flow into capillary beds that are slightly larger and contain rings of smooth muscle called sphincters

pre-capillary sphincters

found on metarterioles and are used to regulate blood flow into capillaries and low pressure in order to prevent damage

• if unregulated, all of the blood in the body could fit in our capillaries

• are typically closed unless tissue requires nutrients or needs to get rid of waste

• when closed, blood flows through the thoroughfare channels and into the venuoles

What does Capillary exchange involve

involves the movement of substances from the blood in the capillaries to the tissue or interstitial fluids or vise versa

• capillaries to tissue exchanges o2, hormones and nutrients

• Tissue to capillaries exchanges CO2 and waste

what does the movement of substances depend on

depends on the size of the molecules

• hydrophobic molecules/lipids soluble molecules like gases can diffuse across membranes (continuous)

• Glucose, AAs use channels in facilitated diffusion

• larger molecules need to pass through fenestrations

• water can travel via osmosis

diffusion definition

the movement of molecules across the cell membrane from high to low concentration

• o2 diffuses into tissue

• CO2 diffuses into blood

Veins definition + types

vessels that bring blood back towards the heart ( not alway deoxygenised)

• have thin walls with large lumens due to their lower pressure compared to arteries

• includes Venules, small veins and large veins

• low pressure as the cappilaty sphincters lower the pressure to prevent capillary damage

Venules: features and structures

the smallest at less than 50 micrometers form of veins that drain capillary beds

• has an endothelium with a basement membrane with few smooth muscle cells

• muscle cell number increases as diameter increases

Small veins features and structure

the vessel where all of the venules merge that have thicker walls with developing smooth muscle cells

• endothelium + continuous layer of smooth muscle

Large veins

veins increase in size as they get closer to the heart, causing them to hold more and more blood

• expand easily to fill with blood

• if veins are more than 2 mm in diameter they have valves to prevent blood flow

Valves

a unidirectional opening in a vein that prevents flow from flowing backwards as it travels back to the heart

• open due to pressure from below and close due to pressure above

• made of thin folds of the Tunica intima

Veins - tunica composition

TI

• smooth endothelium

• no elastic membrane

TM

• thin smooth muscle with collagen fibres

• no elastic membranes

TA contains collagenous CT + elastic fibres and smooth muscle

Blood flow definition

The amount of blood passing through a vessel organ, or tissue (ml/min)

• facilitates transportation, regulation and protection

haemodynamics definition

the study of the movement of blood through the body based on pressure, resistance and cardiac output

• the movement of blood is determined by the volume of blood being pumped, the pressure the blood is under, and the force blood has to oppose to move foreward

arterial blood flow

the amount of blood passing through an artery per minutes

• ensure the efficient transportation of O2

• too high could damage the blood vessels and organs

• Too low leads to inadequate delivery

what is resistance + influences

the force at which the blood has to overcome to pass through a vessel

• influenced by vessel lumen diameter ( contriction and dilation), vessel length and blood viscosity

Resistance: vessel diameter

The size of the lumen can depend on the type of vessel and is controlled by constriction and dilation which can decrease or increase the size of the lumen

• increase lumen = less blood contact with the wall, less friction and resistance and increased blood flow

• Decreased Lumen = more contact with vessel wall, greater friction / resistance and decreased blood flow

Resistance: vessel length

The longer the vessel, the greater the resistance and the lower the blood flow

• due to an increase in the surface area of the vessel which means more friction

Resistance blood viscosity

The thickness of the blood that can cause resistance through interactions between components in the blood and the vessel wall

• Low viscocituy = less components and less resistance = high blood flow

• High viscosity = more components and more resistance = low blood flow

what is blood pressure

the pressure exerted against the wall of the vessel

• When measured we refer to arterial pressure

• expressed as systolic / diastolic

systolic vs diastolic

systolic: the highest pressure against arteries that occurs when the heart contracts ( systemic arteries)

• safe levels at approximately 120mmHg

Diastolic: lowest arterial pressure when the heart is relaxing

• safe = 80 mmHg

what is venus return + involved factors

The system through which blood from capillary beds returns to the heart is a low-pressure system ( often moves against gravity unless returning from the top half of the body)

• regulated by pressure differnces and muscular and respiration pump

how do pressure differnces help us pump blood back to the heart

Blood flows from high to low pressure, which means the pressure in the artery is higher than the veins, and the pressure in the veins must be higher than in the right atrium (when relaxed)

• blood moves in veins when the heart is relaxing (pressure in atrium = or is approaching 0)

• creates a pressure gradient at which blood moves across

Muscular and respiratory pumps

Muscular pumps: muscles on either side of a vein that, when they contract, put pressure on the blood in the vein, causing it to move to the heart

• pushes blood through valves

Respiratory Pumps: During inhalation the diaphragm moves down, placing pressure on the abdominal veins