BIOL 2304
Blood
The Circulatory System
Anatomy – enclosed muscular pump and tubes filled with blood.
Blood
Heart
Blood vessels
Physiology
Supply body tissues with oxygen and nutrients and remove waste from body tissues
Deliver hormones to target organs
Regulate body temperature
Blood
Composed of liquid and cellular portions
Plasma
Water
Proteins (ie: hormones)
Electrolytes (ions)
Formed elements – cellular portion of blood
Red blood cells
White blood cells
Platelets
Blood
Plasma – 55% of blood
RBC – 45% of blood (Hematocrit)
Hematocrit - The ratio of the volume of red blood cells to the total volume of blood
WBC – <1% of blood
Platelets – <1% of blood
Plasma Composition
90%Water
Transport medium
Carries heat
Electrolytes
Membrane excitability
Nutrients, wastes, gases, hormones
Transported in blood
6-8% Plasma proteins
Albumins – contribute to osmotic pressure
Globulins – clotting factors, antibodies
Fibrinogen – inactive precursor for fibrin
RBC Structure and Function
Biconcave discs
Provides larger surface area for diffusion of O2 across the membrane
Thinness of cell enables O2 to diffuse rapidly between the exterior and innermost regions of the cell
Flexible membrane
Allows RBCs to travel through narrow capillaries without rupturing in the process
Hemoglobin
Iron containing pigment found only in RBCs
Consists of 2 parts
Globin portion
Protein composed of four highly folded polypeptide chains
Heme groups
Four iron-containing nonprotein groups
Each is bound to one of the polypeptides
Formation dependent upon Vitamin B12
WBC Structure and Function
Colorless and larger than RBCs
Protect body from microorganisms
5 different types of circulating leukocytes, either Granulocytes or Agranulocytes
Neutrophils
Eosinophils
Basophils
Monocytes
Lymphocytes
Neutrophils
Most numerous WBC
Phagocytize and destroy bacteria
Nucleus—has two to six lobes
Granules pick up acidic and basic stains
Eosinophils
Compose 1–4% of all WBCs
Play roles in ending allergic reactions, parasitic infections
Basophils
About 0.5% of all leukocytes
Nucleus—usually two lobes
Granules secrete histamines
Function in inflammation mediation
Similar in function to mast cells
Lymphocytes
Compose 20–45% of WBCs
The most important cells of the immune system
Nucleus—stains dark purple
Effective in fighting infectious organisms
Act against a specific foreign molecule (antigen)
Monocytes
Compose 4-8% of WBCs
The largest leukocytes
Nucleus—kidney shaped
Transform into macrophages
Phagocytic cells
Leukocytes
Platelets
Cell fragments
Lack nuclei
Have organelles and cytosolic enzymes for generating energy and synthesizing secretory products
Involved in blood clotting (thrombosis)
Hematopoiesis aka Hemopoiesis
Hematopoiesis - the formation of blood cells in the living body (especially in the bone marrow).
All blood cells originate in bone marrow.
All originate from one cell type.
Blood stem cell (pluripotent hematopoietic stem cell)
Lymphoid stem cells
Give rise to lymphocytes
Myeloid stem cells
Give rise to all other blood cells
Heart - Location of the Heart
Largest organ of the mediastinum
Located between the lungs
Apex lies to the left of the midline
Base is the broad posterior surface
Anatomy of the Heart
Pericardium—two primary layers
Fibrous pericardium
Strong layer of dense connective tissue
Serous pericardium
Formed from two layers
Parietal layer of the serous
pericardium
Visceral layer of the serous
pericardium
Layers of the Heart Wall
Epicardium
Visceral layer of the serous pericardium
Myocardium
Consists of cardiac muscle
Muscle arranged in circular and spiral patterns
Endocardium
Endothelium resting on a layer of connective
tissue
Lines the internal walls of the heart
Myocardium
Forms a thick layer called myocardium
Striated like skeletal muscle
Contractions pump blood through the heart and into blood vessels
Contracts by sliding filament mechanism
Cardiac Muscle Tissue
Cardiac muscle cells
Short, branching, with one or two nuclei
Cells join at intercalated discs
Complex junctions that connect one cell to the next
Intercalated disc - an undulating double membrane separating adjacent cells in cardiac muscle fibers.
Intercalated discs support synchronized contraction of cardiac tissue
Cells are separated by delicate endomysium
Binds adjacent cardiac fibers
Contains blood vessels and nerves
Gross Anatomy of the Heart
Atria - Two thin, upper chambers that receive blood
Right atrium receives oxygen poor blood from body
Left atrium receives oxygen rich blood from lungs
Ventricles - Two thick, lower chambers that pump blood
Right ventricle pumps oxygen poor blood to lungs
Left ventricle pumps oxygen rich blood to body
Left and right sides of heart separated by septa
Septa - thin walls or partitions between the internal
chambers (interventricular septum)
Structure of Heart Wall
Left ventricle —
three times thicker than right
Exerts more pumping force
Because it requires more force to send blood
to the body than to the lungs
Flattens right ventricle into a crescent shape
Right Atrium
Receives oxygen poor blood from superior and inferior vena cava
Pectinate muscles
Ridges inside anterior of right atrium
Crista terminalis
Landmark used to locate veins entering right atrium
Fossa ovalis
Depression in interatrial septum – a remnant of foramen ovale
Right Ventricle
Receives blood from right atrium through the tricuspid valve
Pumps blood into pulmonary circuit via pulmonary trunk
Internal walls of right ventricle
Trabeculae carneae
Papillary muscles
Chordae tendineae
Pulmonary semilunar valve
Located at opening of right ventricle and pulmonary trunk
Left Atrium
Makes up heart’s posterior surface
Receives oxygen-rich blood from lungs through pulmonary veins
Opens into the left ventricle through
Mitral valve (left atrioventricular valve/bicuspid valve)
Left Ventricle
Forms apex of the heart
Internal walls of left ventricle
Trabeculae carneae
Papillary muscles
Chordae tendineae
Pumps blood through systemic circuit via
Aortic semilunar valve (aortic valve)
Heart Valves
Each valve composed of
Endocardium with connective tissue core
Atrioventricular (AV) valves
Between atria and ventricles
Aortic and pulmonary valves
At junction of ventricles and great arteries (pulmonary and aortic arteries)
Vasculature of the Heart
Vasculature of the Heart
Functional blood supply
Coronary arteries
Arise from the aorta
Located in the coronary sulcus
Main branches
Left and right coronary arteries