Loyola University Medical Education Network Part 5: Blood and Capillaries

Slide 51

Normal cells of blood as seen in a blood smear. This slide shows many red blood cells and one neutrophil (or polymorphonuclear leukocyte). Neutrophils characteristically have a multi-lobed nucleus and very fine, neutral-stained cytoplasmic granules. These cells migrate out into the connective tissue and become phagocytic and provide a first line of defense in acute infections.

Slide 52

Eosinophil -- with quite large, regular, refractile, eosinophilic (pink) cytoplasmic granules, and a bilobed nucleus. Eosinophils congregate in connective tissue in allergic reactions.

Slide 53

Basophil -- with very dark, coarse, basophilic (purple-blue) granules in the cytoplasm surrounding the lobed nucleus. The granules contain principally histamine and heparin. Basophils are activated in response to immunologically mediated hypersensitivity reactions.

Slide 54

Small lymphocyte - only a little larger than a red blood cell, it has only a thin rim of pale cytoplasm around a darkly stained round nucleus. Its function is related to the body's immunological defenses. Scattered among the r.b.c.'s are some very small clumps of platelets, which are necessary for the clotting of blood.

Slide 55

A large lymphocyte circulating in the blood. The nucleus is characteristically round and dark, but there is more cytoplasm than in the typical "small" blood lymphocyte.

Slide 56

Monocyte - the largest of the leukocytes, it has quite a bit of bluish cytoplasm, surrounding a typically kidney-bean-shaped nucleus. When out in connective tissue, this cell becomes a macrophage (histiocyte).

Slide 57

EM of neutrophil, showing its multi-lobed nucleus. The many electron dense lysosomes in the cytoplasm are characteristic of a phagocytic cell.

Slide 58

EM of eosinophil cutting through bilobed nucleus. Notice the typical "cat's-eye" appearance of the cytoplasmic granules with the dark crystalloid band in the middle of each one. (Such bands do not appear in human eosinophils.) These granules, banded or not, contain hydrolytic enzymes and are lysosomal in nature.

Slide 59

EM of basophil showing dense granules reminiscent of those of mast cells. At one time it was thought that the basophil of the blood became the mast cell of connective tissue, but most work now indicates that these are two different cell lines ... though their granules contain basically the same secretory substances.

Slide 60

EM of monocyte with many lysosomes in an active-looking cytoplasm. Again, the lysosomes indicate potential for phagocytic activity.

Slide 61

EM of lymphocyte -- rather a nondescript looking cell considering its great functional importance. Notice the cytoplasmic process to the right and relate it to the appearance of lymphocytes in the next two pictures.

Slide 62

Scanning electron micrograph of lymphocyte with many cytoplasmic extensions.

Slide 63

Scanning electron micrograph of lymphocyte with relatively smooth surface. Differences in cell surface presumably represent differences in cell activity at the moment. At one time such visible differences were thought to provide a distinction between B cells and T cells, but recent work does not substantiate this.

Slide 64

Scanning EM of red blood cells. Normal ones have the typical biconcave disc shape. The "spiny-looking" ones are crenated because of loss of cytoplasmic fluid to a hypertonic environment.

Slide 65

Red blood cells lined up in rouleaux (stacks). This vessel is in bone. Such clumping of cells suggests rather stagnant flow, as was probably the case in this postmortem tissue.

Slide 66

Longitudinally cut capillaries running in the connective tissue between cardiac muscle cells. Note the very thin endothelial lining of the vessels. Notice too that the capillary diameter is essentially that of the red blood cell. Several r.b.c.'s can be seen in transit here. Their shape is plastic, responding to surrounding pressures, but cells are traveling independently. Compare their appearance with the stacked cells on the previous slide.

Slide 67

Capillaries in the connective tissue supporting cardiac muscle cells, this time cut in cross-section. Good examples lie in the upper left and lower left of the field. Look for a small thin-walled circle with a dark, crescent-shaped endothelial nucleus on one side. The rest of the thin circle of wall is composed of endothelial cytoplasm.

Slide 68

Small blood vessels of various sizes in areolar connective tissue. The two cross-cut capillaries at center contain erythrocytes and show an endothelial nucleus at the rim. The largest vessel, at extreme center right, is a venule. All of the vessels shown here are thin-walled and capable of fluid and ion exchange with the surrounding connective tissue fluid. In addition, leukocytes can squeeze between endothelial cells of the walls of such vessels (by diapedesis) and enter the connective tissue. Only when they leave the bloodstream do they assume their active roles.

Slide 69

EM of cross-cut capillary lying between skeletal muscle cells. Note a peripheral muscle nucleus at the top of the micrograph. A thin basal lamina surrounds the endothelium as well as the muscle cells. CL=capillary lumen; CJ=cell junction; G=glycogen particles; M=mitochondria; N=nucleus of endothelial cell; PV=pinocytotic vesicles.

Slide 70

Two EM views of fenestrated endothelium. In the section at left, through the cytoplasm of an endothelial cell, fenestrations are represented whenever the inner and outer cell surfaces meet in a thin line. In the picture at right a tangential cut through the surface of an endothelial cell shows multiple round fenestrations.

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John A. McNulty Last Updated: August 12, 1996