Circulatory System: Components and Functions

Components of the Circulatory System

• The three basic components of the circulatory system are blood, the heart, and blood vessels.
• Blood transports dissolved and suspended materials like oxygen, carbon dioxide, nutrients, electrolytes, hormones, and metabolic waste.
• The heart is a pump that generates cardiac output with a pressure gradient, which is needed for blood flow.
• Blood vessels form a complex network of conduits (or portals) to transport blood distributed from the heart to all parts of the body and back.

Functions of the Circulatory System: Transportation

• The circulatory system transports respiratory gases, like O2 and CO2.
• Digestion products are carried to the liver, tissues, & organs.
• Metabolic wastes are carried to the kidneys for excretion.

Functions of the Circulatory System: Regulation

• Hormones are transported to target tissues.
• Homeostasis is maintained by regulating pH and electrolyte balance.
• Blood can be diverted to cool or warm the body.

Functions of the Circulatory System: Protection

• Haemostasis prevents bleeding through blood clotting.
• The immune system protects against pathogens by transporting leukocytes, cytokines, and complement.

Blood Characteristics

• Blood is a specialized liquid connective tissue designed for short and long-range transport.
• There is material transport between cells, and between the cells and the external environment.
• Total blood volume is dependent on body size, fluid and electrolyte concentration, and amount of adipose tissue.
• Blood accounts for ~8% of body weight.
• The volume of blood is 5-6 liters in males, and 4-5 liters in females.

Composition of Blood

• Blood consists of blood cells suspended in plasma.
• Plasma accounts for approximately 55% of blood volume.
• Plasma is a straw-colored liquid that is ~92% water and contains dissolved solutes.
• Plasma solutes include specialized proteins (~7% albumin, globulin), electrolytes (sodium, calcium, chlorides), nutrients, hormones, and metabolic wastes.
• Formed elements account for ~45% of blood volume.
• Formed elements contain red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes), which aren't cells.

Gender Differences in Blood Composition

• Erythrocytes account for 45% of blood volume in males on average and 42% in females.
• Buffy coat (leukocytes and platelets) account for 0.4-0.5% of blood volume in males, and 0.2-0.4% in females.
• Plasma accounts for 54% of blood volume in males and 57% in females.

Constituents of Plasma

• Albumins are major plasma constituent.
• Albumins account for most of the plasma proteins.
• Globulins are antibodies.
• Globulins transport water-insoluble hormones, lipids, and vitamins.
• Fibrinogen is essential for coagulation and forms the stable blood clot by converting to fibrin.
• Electrolytes such as sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), chloride (Cl-), bicarbonate (HCO3-), and sulphate (SO₄) are needed for cell function.
• Other proteins are enzymes, coenzymes, and hormones.
• Organic nutrients include lipids, cholesterol, carbohydrates, and amino acids, provide energy for cell activities
• Organic waste products include urea, uric acid, creatinine, bilirubin, and ammonium ions (NH4+).

Formed (Cellular) Elements

• Red blood cells (erythrocytes) contain hemoglobin for O2/CO2 binding and transport.
• White blood cells (leukocytes) are mobile units of the body’s immune defence system
• Leukocytes transport in blood to sites of injury or invasion by pathogens.
• Platelets (thrombocytes) are important in hemostasis, and arrest bleeding an injured vessel

Erythrocytes (RBCs)

• Erythrocytes are smooth, round, flexible biconcave discs lacking nuclei, mitochondria, and most organelles.
• Erythrocytes transport O2 and CO2.
• Erythrocytes are the most abundant cell type in blood.
• Typical values for males = 5.6 – 6.2 x 10^6 /μL, females = 4.2 – 5.4 x 10^6 /μL, infants = 5.0 – 6.5 x 10^6 /μL.
• Erythrocytes are formed in red bone marrow, stimulated by erythropoietin in the kidney.

Hemoglobin

• Hemoglobin is an iron-containing molecule that binds O2 loosely and reversibly.
• Hemoglobin is synthesized and packed into RBCs during cell development.
• A hemoglobin molecule has two each of  &  polypeptide chains (globin moiety), and four iron-containing haem prosthetic groups
• Each hemoglobin molecule carries four O2 molecules.
• Hemoglobin is also used for CO2 transport, and offers pH buffering as blood flows through tissues & organs.

Leukocytes (WBCs)

• There are two main categories of leukocytes:
  • Granulocytes (70%) contain granules in the cytoplasm which consist of Neutrophils (65%), Eosinophils (4%) and Basophils (1%)
  • Agranulocytes (30%) have no granules which consist of Lymphocytes (25%), and Monocytes (5%)
• They function as defense agents and protect against tumors, bacteria, viruses, and parasitic infections.

Granulocytes

• Neutrophils are phagocytic specialists that are the first line of defense against invading microbes.
• The multiobed nucleus has small purple granules in the cytoplasm, and have a short life-span in circulation (6-8h).
• Neutrophils ingest, trap, and destroy pathogens, clean cellular debris, and act to slow or localize microbial infection
  • They increase in active and acute bacterial infections (we do blood tests to check).
• Eosinophils defend against parasitic infections by attaching to and secreting substances to kill parasitic worms
• They are large, phagocytic, bi-lobed nucleus with large red granules in cytoplasm.
• Eosinophils also act to moderate allergic reactions, and ↑ in internal parasitic infestations & allergic conditions (asthma & hay fever).
• Basophils synthesize, store, and release histamine and heparin and play a major role in allergic and hypersensitivity reactions also seen in infections.
• Have a deeply indented nucleus with large, dark blue granules.

Agranulocytes

• Lymphocytes (B and T cells) have a large, dark spherical nucleus with a thin rim of light blue cytoplasm, and play a major role in immune system function.
  • They increase in chronic infections. B cells produce antibodies to target & mark invading bacteria & viruses to ‘kill’ (adaptive humoral-mediated immunity).
  • T cells that produce lymphokines include T helper and T cytotoxic which are directed to attack & kill virus and infected or tumor cells (cell-mediated immunity).
  • Natural killer cells attack and kill virus-infected and tumor cells.
• Monocytes are large, round/oval/kidney-shaped nucleus that phagocytize to engulf and kill pathogens.
  • Monocytes have abundant agranular cytoplasm, and are key in the immune system.
  • ↑ in acute infections and scavenge dead pathogens.

Platelets (Thrombocytes)

• Platelets are granule-rich packages in circulatory system.
• They have a key role in circulatory system.
• A key role is to maintaining the integrity of endothelial lining via activating hemostasis by sending factors that stop the arrest of bleeding.
• Granules will contain serotonin (5-HT), Ca2+, enzymes, ADP and platelet-derived growth factor (PDGF).

Platelets and Haemostasis

• Vascular injury exposes collagen & basement membrane proteins which causes platelet adhesion, activation & aggregation.
• Activated/aggregated platelets release pro-aggregatory mediators - ADP & thromboxane A2, and thrombin generation by coagulation.
• Clot stabilization occurs with mesh-like fibrin deposition.

The Heart: Gross Anatomy

• The heart is a hollow, muscular organ about the size of a clenched fist.
• Locates in the mediastinum in the midline between the sternum (breastbone) and the vertebrae (backbone).
• The heart is surrounded by a double-layered membrane called pericardium.
  • The inner, pericardium (visceral) covers entire heart (epicardium).
  • The outer, pericardium (parietal) is attached to the great vessels, sternum, and diaphragm.
  • The Pericardial cavity includes 30–50 ml serous fluid.

The Heart: As a Pump

• The heart is a 4-chambered muscular organ functioning with two separate pumps.
• Each pump can be separated by upper chamber (atrium) and a lower chambers (ventricle).
• Each upper chamber then opens to a lower chamber through a valve - ensure the blood can only flow one direction (tricuspid and mitral).
• Left and Right pumps are separate by a muscular portion (septum).

Right-Sided Pump details

• This pump is concerned with pulmonary circulation and gaseous exchange - receive de-oxygenated blood.
• Pumps to the lungs for re-oxygenation & CO2 removal.
• Lower chambers open to Pulmanory artery through a pulmonic valve.

Left-Sided Pump details

• Pumping relies on the need for systemic circulation and delivering O2, nutrient supply.
• Receives re-oxygenated blood from the lungs then Pumps to systemic circulation.
• Lower chambers opens into aorta a aoritic valve

Blood Vessels of the Heart

• TWO main types; The Great Cardiac Vessels which help carry blood within hear, and back from systemic/pulmonary circulations
  • Includes; Superior and inferior vena cava which contain largest vessels returning the deoxygenated blood which is sent to the right atrium.
  • Includes; Pulmanory Artery - accepts output of the right ventricle, has peek systolic ~ 25 mmHg
  • Includes; Pulmonory Veins largest vessels returning oxygenated blood to left atrium
  • Includes; AORTA - accepts output of left ventricle, and sustains highest systolic ~ 140mmHg

Coronary Vessels

• Coronary Circulation supplies blood to the heart. Aorta supplies blood which is then brought to cardiac muscle tissue. These then send blood to right atrium. a) left, and right coronary arties b) coronary sinus, Great / Middle / Anterior & Posterior cardiac veins, Thebesian veins

Heart Valves

• Valves are strategically placed to promote one direction flow of openings.
• They ensures that only one direction of the openings, which is used to prevent backflow of blood and ensures unidirectional blood flow.

Atrioventricular Valves (AV)

   - Separates Atrium and Venticle where there may be differences between each side.
   - There is a tricuspid valve between Right atrium and ventricle.
   - There are Bicuspid and Mitral valve Between and Left at and ventricle
Semilunar - half moon shaped valves are used to prevent blood pooling in areas.
   - Aortic valve - between the left vetricle and aorta.
   - Pulmonic valve - between right the venticle and pulmonic artery.

Heart Wall

• The heart's wall has three layers:
  • An innermost Endocardium which is an innermost and thinn lining of endothelial cells where blood clots are prevented.
  • A middle Myocardium, composed of cardiac muscles which also forms bulk.
  • Then there is a outer Epicardium with protective component and has epicardial coronary vessels.

Cardiac Cell Types

• T wo main specilized types within heart where contractions can take place by help of muscle.
  • Contractile cells Cardiac must cell takes up 99 %. With Interlacing bundles arranging around circumferemce they act electricall quite not normally doing it.

electrical/autorhymic will start initiating.

Cardiac Resting Potential details

• Inside polarization is dependent on ionic concentrations across cell
• These are dependent and changing - opening or closing depending on both
• POTASSUM Channels are most prominent
• automaticity and are prone to depolarization

Excitablilty

• Ability to respond electrically and through action potentital
  • 2 Types include slow and fast AP
    • Fast - higher conductance, not prone to be blocked
    • Slown more susceptable to failures.

Cardiac Action Potentials

• Fast, used in ventricles
• transient and leaky
• Slow, are present within the nodal
  • fast Na channels

Cardiac Cell Properties Details

• inability to not to produce more than a stimulation in a period
• with time, that has been elicited, and this protects against both excitation
• recovery in time

Muscle Cell Contraction

• Automatic - some cells that are not can intiate spontaneously
• In SA node, you are taking higher periroity with that region.
  • some cells do have this abilotiy to work more frequently with cells

Heart Control

• controlled between, sympathetic and other functions within control
  • SA will provide some form of beat depending on the situation

Excitation Heart

• naturally beats spontanoeously and ryhtimcally
• in specific order - from the atri and AV with conduction
• delay gives chance for the area ot contract prior, otherwise ventricles will contract at once with SA and Av to purkinje fibers.

ECG/EKG Properties.

• Electrical measurements and current
  • Generated due muscle delprozation /repozaration
  • 6 leads are the way to record this - standard 12 reads

EKG

• T -3 distincts, 1 - which represnts depolarization with Atrial 2 then there is hye repolization within complex which goes down to 3 - repesnets Ventricle repozlaizaiton

Heart contractions

• with action of the heart the muscle is pumped

• Desmasomes help with cell junction

Cardiac Cycle and Function

• it pumps rythic ally
• both the empting
• isocolumetric contraction and during ejction

Blood Vessels

• these is a closed system to have things flow

• artiers, and

• arterioles

• capilliaies helps with exhange

• With some help of muscle contration Veins and these all assist returning blood.

Vessels

• walls can and do vary from each
  • 3 Layers include external and meddia with inner
  • intima with inner, which is squames endothelium

arteries have alot of roles for being able transmit blood from an area, used in vasocontriction small muscles are used to facilitate organ functions

elastic vs muscular arteries

• there are different for both
  • elastic provides higher force, with numerous layers, used to help facilitate movement. ex. pulmonary - muscular, has less elastic, but is thicker. not that much changes. ex. femoral

Arterioles

smaller then branches to allow different flow depending on the situation with muscle movement, and vessel radius, controlled via different control.

Capillies

• small denses which allow exchange + nutrients with diffusion and small walls (end) -walls are perforated for small molcules sphinctetors and blood flow are regulated via caps these depend on size of water-filled poles

Caplliers

• fenested larger holes with permeability, with kidneys, intestines and ectocrine blands d) Disconitinous endothelial are discontingous and very porous - liver, or marrow

Capialr

• Passively transported

Bulk flows helps with reabospriton of materials. These determine blood to flow which comes with pressures

Veins

low areas,

venules small vienss, then large

The great veins

high flow for that

One ways valves are made and will ensure forward with muscle movement.

Blood stream

• Systolic ( high exertion)
• Diametr - low exertion

Regulation

• high output with HR

• blood volume

• blood pressue maintin is cruicially used. a1 - and ect.

  will also regulate with renal by h20 adn Na. shortened controlls in different seconds

• the heart or vessel is controlled from auto/pns ily will reanl mechansima for the renal and water.

• adjustments is very necessary to keeep system functioning