Aims

• Lymphatics.

• Blood composition

• Blood clotting

• Readings; Sherwood, Chapter 10 & 11; Robbins, pages 84-90

Sherwood’s Human Physiology 10-25 (10-24 6th Edition)

Lymphatics• Carry proteins and large particles out of

tissues.• 1/10 of fluid that leaves the capillaries enter

the lymphatics.• Lymph fluid is derived from excess interstitial

fluid.

Sherwood’s Human Physiology 10-25 (10-24 6th Edition)

Lymphatic Capillary• Valves

– Overlap of the endothelial cells allow for large particles to enter lymphatics.

– High pressure inside the lymph vessel will seal it.

Lymph Flow

• Interstitial fluid pressure– Increase in Interstitial fluid pressure => ____________

lymph flow.

• Lymphatic Pump– Smooth muscle cells around the lymph vessels contract

in response to stretch (primary force)– Contraction of skeletal muscle (secondary force)– Internal valves function similar to veins to prevent

backflow.

Guyton’s Textbook of Medical Physiology 16-10

Lymph Flow

• Lymph flow increases as the interstitial pressure increases.

• Plateau is due to the compression of larger lymphatic vessels.

Sherwood’s Human Physiology 10-26 (10-25 6th Edition)

Lymphatic System• Main Functions

• Return excess filtered fluid.

• Defense against disease.

• Transport of absorbed fat.

• Return of filtered protein.

Sherwood’s Human Physiology 10-27 (10-26 6th Edition)

Edema• Accumulation of _____________________

fluid.

• Reduced conc. of plasma proteins.– Decreased colloid pressure

• Increased capillary permeability.• Increased venous pressure.• Blockage of lymph vessels.

Sherwood’s Human Physiology Table 11-1

Blood Composition

• Plasma is the non-cellular portion.– Water– electrolytes– proteins

Sherwood’s Human Physiology Table 11-1

Blood Composition

• Cellular portion – leukocytes– erythrocytes– platelets

Sherwood’s Human Physiology 11-1

Blood Composition• Separate blood by centrifugation

• Plasma is the liquid top portion.– 55%

• Cellular portion is the bottom half.– “Buffy coat”

• leukocytes• platelets

Blood Plasma• Water

– Transport medium.

– Carries heat.

• Electrolytes– Ions necessary for membrane potential regulation (Na+, K+, etc.).

– pH buffer.

– Osmosis regulation between outside and inside cells.

• Proteins– Transportation (Albumin).

– Blood clotting (Fibrinogen).

– Immunity (Ig).

– Colloid osmotic pressure

Blood Cells

• Leukocytes– ___________________.

• Erythrocytes– Transport O2 and some CO2.

• Platelets– Plugging and clotting.

Sherwood’s Human Physiology 11-2

Erythrocytes (RBCs)

• Functions– Transport hemoglobin (which carries O2).

– Convert CO2 to bicarbonate ion (HCO3-)

via carbonic anhydrase.

– Acid-base buffering.

Sherwood’s Human Physiology 11-3

Hemoglobin A• Most common form

• 4 subunits– 2 peptides

– 2 peptides

– each contain a _________________ group which has an iron atom.

– The iron atom interacts with two oxygen atoms (one oxygen molecule).

Guyton’s Textbook of Medical Physiology 32-1

Location of Erythrocyte Production

• After birth the bone marrow is the source of erythrocytes.• Initially, the bone marrow of every bone produces erythrocytes,

with time that is narrowed to membranous bones.

Guyton’s Textbook of Medical Physiology 32-4

Erythropoiesis

• Production of erythrocytes

• Erythropoietin – circulating hormone– 90% by

________________– 10% by liver– Mediates hypoxia

induced erythrocyte production

Sherwood’s Human Physiology 11-4

Regulation of Erythropoiesis

• Decreased blood oxygenation results in increased erythropoietin production.

• Increased erythropoietin production results in more RBCs.

• More RBCs results in increased blood oxygenation.

1010 cells destroyed/hour

1010 new cells made/hour

RBCs in the circulation

~1013

Bone Marrow

Reticulo-endothelial

system

Iron

Amino acids

Iron

Amino acids

From DietIron

Amino acids

Stool and urine

RBC Life Cycle

Abnormal Hematocrit

• Anemia– ____________________________ RBC’s (Nutritional, Pernicious,

Aplastic, Renal, Hemorrhagic, Hemolytic)• Polycythemia

– Increased RBC’s (Primary and Secondary)

Sherwood’s Human Physiology 11-5

Hemostasis• The regulation of blood fluidity and clotting in

response to a broken blood vessel (ie. stop the bleeding).– Under normal conditions blood is maintained in a

fluid clot-free state.– At the site of a vascular injury this state is rapidly

changed with the formation of a platelet plug.

• The opposite of normal hemostasis is thrombosis in which a blood clot forms and occludes an uninjured or mildly injured blood vessel.

Hemostasis• The 3 components of hemostasis are:

– The vessel wall

– ________________________

– The coagulation cascade

• The 3 major steps of hemostasis are:

– Vascular Spasm (initial response, constricts)

– Platelet plug formation

– Blood coagulation (clotting)

Platelets• Oval discs 1-4 m in diameter.

• No nuclei.

• 1/2 life of 8-12 days.

• Play a major role in hemostasis.

• Can synthesize important proteins: ADP, Thromboxane A2, Fibrin stabilizing factor.

• Coat glycoprotein repels normal endothelium, but adheres to exposed collagen on the injured vessel walls.

Sherwood’s Human Physiology 11-9

Origin of Platelets

• Derived from megakaryocytes in the bone marrow.

Sherwood’s Human Physiology 11-10

Platelet Plugs

• Accumulation of platelets to seal small holes in a vessel wall.

Sherwood’s Human Physiology 11-10

Formation of Platelet Plugs

• Step 1– When platelets see damaged vessel wall they adhere to it

and swell.

• Step 2– They release granules containing ADP and thromboxane

A2 (also a vasoconstrictor) which activate nearby platelets to also adhere.

Next Time

• Blood clotting (cont.).

• Regulation of blood pressure.

• Regulation of blood volume.

• Reading; Sherwood, Chapters 10 &11, Chapter 15 pages 569-570 ; Robbins, pages 84-90

Objectives

• Describe the structure and function of lymphatics.

• Know the components of blood (plasma and cellular components).

• Describe the function of these blood components.

• Describe erythropoiesis and its regulation.• Know what hemostasis is, as well as its

components and steps involved.• Describe how platelet plugs form.