Cardiovascular System Cardiovascular System Components Blood Blood - - PowerPoint PPT Presentation

Cardiovascular System

Cardiovascular System

• Components

– Blood – Blood Vessels – Heart

• General Functions

– Transport – Regulation – Production/Synthesis – Movement – Protection

Blood

• Why/How does blood flow?
• Functions of blood

– Carries respiratory gases, nutrients, and hormones – Helps body regulate temperature

• Blood volume

– Males: 5‐6 liters – Females: 4‐5 liters

Overview: Blood Composition

• Connective Tissue
• Contains cellular and liquid components

– formed elements – plasma

• Hematocrit

– Males:

• 47% ± 5%

– Females:

• 42% ± 5%

Blood Plasma

• Straw‐colored, sticky fluid portion of blood
• Approximately 90% water
• Contains ions, nutrients, wastes, and proteins

– Three main proteins

• Albumin, globulins, and fibrinogen

Formed Elements

• Blood cells

– Erythrocytes (erythros = red, kytos (now cyte) = hollow cell) – Leukocytes (leukos = white) – Thrombocytes (thrombus = clot)

Erythrocytes – Red Blood Cells (RBCs)

• Oxygen‐transporting cells – 7.5 µm in diameter
• Most numerous of the formed elements

– Females: 4.3–5.2 million cells/cubic millimeter – Males: 5.2–5.8 million cells/cubic millimeter

• Have no organelles or nuclei – why?

Why is the size important?

Erythrocytes – Red Blood Cells (RBCs)

• Respiratory Pigment: Hemoglobin
• Biconcave shape – 30% more surface area
• Live 100–120 days
• Originate in the bone marrow

– Production is called erythropoiesis

Why is the shape important? Form rouleaux in capillaries… also disorder if appears in normal blood smear.

Hemoglobin

3‐dimensional structure

• f hemoglobin.

The four subunits are shown in red and yellow The heme groups in green.

Leukocytes – White Blood Cells (WBCs)

• 4,800–11,000/cubic millimeter
• Protect the body from infectious

microorganisms

• Function outside the bloodstream in loose

connective tissue

• Diapedesis – circulating leukocytes leave the

capillaries

• Two types of leukocyte

– Granulocytes and agranulocytes

Granulocytes

• 55 – 80% of WBC count
• Contain multilobed nuclei

– Granules that pick up stain

• Color and nuclear shapes are identifying

characteristics of granulocytes

– Neutrophils – most numerous WBC

• Light colored granular staining cytoplasm
• Nucleus – has two to six lobes

– Eosinophils – compose 1–4% of all WBCs

• Typically bi‐lobed nucleus
• Cytoplasmic granules stain darker orange/red

color

– Basophils – about 0.5% of all WBCs

• Nucleus – usually two lobes
• Granules stain dark blue/purple

– Tends to obscure the nucleus

Agranulocytes

• Lymphocytes

– compose 20–45% of WBCs – Involved in immunity – Effective in fighting infectious organisms Act against a specific foreign molecule (antigen) – Morphology:

• Nucleus – round & stains dark purple
• Cytoplasm – appears free of stained granules
• Size – only slightly larger than erythrocyte

– Two main classes of lymphocyte

• T cells – attack foreign cells directly
• B cells – multiply to become plasma cells

– Secrete antibodies

Agranulocytes

• Monocytes – compose 4–8% of WBCs

– The largest leukocytes – Nucleus – kidney shaped – Cytoplasm – free of stained granules… – Transform into macrophages

• Phagocytic cells

Thrombocytes (Platelets)

• Cell fragments

– Break off from megakaryocytes

• Function in clotting of

blood

– Contain granules in cytoplasm that are involved in hemostasis

Blood Cell Formation

• Process is called hematopoiesis
• 200+ billion new blood cells formed each day
• Location is bone marrow in adults:

– Red marrow – actively generates new blood cells

• Remains in epiphyses, girdles, and axial skeleton

– Yellow marrow – dormant

• Located in the long bones of adults

– Tissue framework for red marrow

• Reticular connective tissue
• Where does hematopoiesis take in the

embryo/fetus?

Hematopoiesis

• All blood cells originate in bone marrow
• All originate from one cell type, the

hemocytoblast (pluripotential hematopoietic stem cell)

• Hemocytoblast differentiates into
• A. Lymphoid stem cells

– give rise to lymphocytes

• B. Myeloid stem cells

– give rise to all other blood cells

Hematopoiesis cont…

• Genesis of erythrocytes

– Committed cells are proerythroblasts – Remain in the reticulocyte stage for 1–2 days in circulation – Make up about 1–2% of all erythrocytes

• Formation of leukocytes

– Granulocytes form from myeloblasts – Monoblasts enlarge and form monocytes

• Platelet‐forming cells from megakaryoblasts

– Break apart into platelets

Disorders of the Blood

• Disorders of erythrocytes

– Polycythemia – abnormal excess of erythrocytes – Anemia – erythrocyte levels or hemoglobin concentrations are low resulting in? – Sickle cell disease – inherited condition

• Results from a defective hemoglobin

molecule

• Erythrocytes distort into a sickle shape

Disorders of the Blood

• Disorders of leukocytes

– Leukemia – a form of cancer – Classified as lymphoblastic or myeloblastic

• Disorders of platelets

– Thrombocytopenia

• Abnormally low concentration of platelets

Early Hematopoeisis

• Blood cells start to develop within the yolk sac

during the first weeks

• Late in the second month stem cells migrate

from yolk sac to the liver and spleen

– Take over until around month 7

• Bone marrow becomes major hematopoietic
• rgan at month 7