Aims
• Lymphatics.
• Blood composition
• Blood clotting
• Readings; Sherwood, Chapter 10 & 11;
Robbins, pages 84-90
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.
Sherwood’s Human Physiology 10-25 (10-24 6th Edition)
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.
Lymph Flow
• Lymph flow
increases as the
interstitial pressure
increases.
• Plateau is due to
the compression of
larger lymphatic
vessels.
Guyton’s Textbook of Medical Physiology 16-10
Lymphatic System
• Main Functions
•
•
•
•
Return excess filtered fluid.
Defense against disease.
Transport of absorbed fat.
Return of filtered protein.
Sherwood’s Human Physiology 10-26 (10-25 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 10-27 (10-26 6th Edition)
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 Table 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
Sherwood’s Human Physiology 11-1
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.
Erythrocytes (RBCs)
• Functions
– Transport hemoglobin (which carries O2).
– Convert CO2 to bicarbonate ion (HCO3-)
via carbonic anhydrase.
– Acid-base buffering.
Sherwood’s Human Physiology 11-2
Hemoglobin A
• Most common form
• 4 subunits
– 2 a peptides
– 2 b peptides
– each contain a _________________ group
which has an iron atom.
– The iron atom interacts with two oxygen
atoms (one oxygen molecule).
Sherwood’s Human Physiology 11-3
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 32-1
Erythropoiesis
• Production of
erythrocytes
• Erythropoietin
– circulating hormone
– 90% by
________________
– 10% by liver
– Mediates hypoxia
induced erythrocyte
production
Guyton’s Textbook of Medical Physiology 32-4
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.
Sherwood’s Human Physiology 11-4
RBC Life Cycle
RBCs in the
circulation
~1013
1010 new cells
made/hour
1010 cells
destroyed/hour
From Diet
Iron
Iron
Bone Marrow
Amino acids
Amino acids
Stool and
urine
ReticuloIron
endothelial
Amino acids
system
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 mm 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.
•
•
•
•
•
Origin of Platelets
• Derived from megakaryocytes in the bone
marrow.
Sherwood’s Human Physiology 11-9
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.
Sherwood’s Human Physiology 11-10
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.