CIRCULATORY SYSTEM 1:
BLOOD AND VESSELS

I.   BLOOD: INTRODUCTION
–  blood is a connective tissue

–  the ground substance is plasma

–  blood cells are called formed elements

1)  erythrocytes (red blood cells):

2)  leukocytes (white blood cells):
3)  platelets (thrombocytes):

II.  ERYTHROCYTES
–  characteristics:

1) shaped like biconcave discs

2)  anucleate

3)  filled with hemoglobin

 

–  function:

III. LEUKOCYTES

–  function:

–  leukocytes are able to slip out of capillary blood vessels (diapedesis)

A.  Neutrophils:
–  most numerous type of leukocyte
–  1.5X larger than erythrocyte
–  cytoplasm has fine pale granules
–  nucleus is multilobed

B.  Eosinophils:
–  about 1.5X larger than an erythrocyte
–  cytoplasm contains prominent granules that stain reddish
–  nucleus is bilobed

C.  Basophils:
–   make up less than 1% of all leukocytes

–  about 1.5X bigger than an erythrocyte
–  cytoplasm contains big granules that stain blue/purplish

–  bilobed nucleus

D.  Lymphocytes:
–  size range:  same size to 2X bigger than erythrocyte
–  cytoplasm lacks (visible) granules
– large, round purple nucleus, surrounded by thin ring of pale blue cytoplasm
–  most located in lymphoid tissues
--  different kinds:  T-lymphocytes, B-lymphocytes and natural killer cells

 

 

E.  Monocytes:
–  about 3X bigger than an erythryocyte
–  cytoplasm lacks (visible) granules
–  pale blue cytoplasm
–  C-shaped or kidney-bean shaped nucleus

IV.  PLATELETS
–  cytoplasmic fragments from a larger cell

–  anucleate
–  very small
–  function:

V.  BLOOD VESSELS: INTRODUCTION

–  arteries take blood AWAY from the heart TO other tissues

*  carry blood_____ in oxygen (exception: pulmonary arteries)

* wall structure:

*  blood pressure             in arteries than in veins

–  veins  take blood back TO the heart

*  carry blood_____ in oxygen and_____ in carbon dioxide (exception: pulmonary veins)

* wall structure:

* lumen size:

*  blood pressure is                in veins

- connecting arteries and veins are tiny vessels called capillaries

–  pathway of blood:
heart –> elastic arteries –> muscular arteries –> arterioles –> capillaries –> venules –> veins –> heart

VI.  BLOOD VESSEL STRUCTURE

A.  Tunica Externa:  outermost layer
*  areolar connective tissue
*  largest layer in veins

B.  Tunica Media:  middle layer
*  circularly arranged smooth muscle fibers
*  sympathetic innervation causes vasoconstriction
*  largest layer in arteries

C.  Tunica Intima:  innermost layer
*  endothelium (simple squamous epithelium) and areolar connective tissue

VII. ARTERIES

A.  Elastic Arteries:

–  vessel wall contains large amounts of elastic protein fibers

B.  Muscular Arteries:

–  diameter ranges from  .3mm - 1cm
– less elastin than elastic arteries, and more smooth muscle in the tunica media

C.  Arterioles:
–  diameter is less than .3 mm
–  tunica media consists of 6 or fewer layers of smooth muscle

VIII. CAPILLARIES
–  vessel diameter is only slightly larger than the diameter of an erythrocyte!
–  tunica intima only
–  capillaries form capillary beds
–  gas/nutrient exchange occurs here!!!

IX.  VENULES AND VEINS

A.  Venules:
–  collect blood from capillaries

B.  Veins:
–  formed when venules unite

–  most (but not all) veins have valves
*  formed from tunica intima

* function:

 

 

 

 

 

–  muscular pumps also help blood be pushed in veins toward heart

 

 

The tunica media is the thickest of the three blood vessel wall layers in a(n):

a.  venule

b.  muscular artery

c.  vein

d.  capillary

e.  none of the above

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