histo lab #7 blood, lymphatics, skin

8/13/2019 Histo Lab #7 Blood, Lymphatics, Skin

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Week of 25 March 2013

Histology Lab # 7 Blood, Lymphatics, Skin

Goals:

1. Review prepared slides:a. Hematopoiesisb. Blood Vesselsc. Lymphatics

1. Lymph Node2. Spleen3. Thymus

d. Integument and Oral Cavity1. Thick skin2. Thin skin3. Tongue

Supplement Pages: 11, 12, 13, and 14

Slides: #49 Hematopoiesis#48 Blood Vessels#51 Lymph Nodes#54 Spleen#55 Thymus#56 Thin Skin#57 Thick Skin#58 Tongue

Background:Blood Vessel Structure

Tunics

Tunica IntimaConsists of a layer of Endothelial cells lining the internal surfaceSubendothelial Layer of connective tissueInternal Elastic Lamina present in arteries

Tunica MediaMostly smooth muscle cells and interspersed fibers: Elastic, Reticular with

proteoglycansExternal Elastic Lamina present in large arteries

Tunica AdventitiaIs an outer layer of connective tissue


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Lymphoid TissuesPrimary: Responsible for the production of all blood cells including

lymphocytes and other cells such as mast cells and macrophages.1. Bone MarrowBone marrow is the largest organ in the body

2. Secondary Lymphoid Organs: Where lymphocytes are maintained,and provide sites for lymphocyte interaction with antigen and each other.These are: Spleen, Lymph Nodes, and less well organized lymphoid

tissues underlying various internal epithelial mucous membranes.These are the Mucosal - Associated Lymphoid Tissue or MALT

In addition, there are Gut associations = GALT, and Bronchial(Respiratory) associations = BALT

3. Tertiary Lymphoid Organs: These are smaller, less well organizedclusters of lymphoid elements such as those associated with the skin.

Those associated with the skin are cutaneous associated lymphoid tissue.

ThymusThe thymus is a flat, bilobed organ in the center of the chest above theheart.

The thymus is enclosed in a connective tissue capsule that invades thebody of the gland and subdivides it into lobes and lobules.

Lobules of the thymus gland have a cortical region and a medullaryregion.

Both the cortical and medullary regions have the same kinds of cells,differing primarily in their stage of differentiation. The medulla containssignificantly fewer cells than the cortical region.

The lobules also contain epithelially derived cells, the Nurse or Reticularcells. These have cytoplasmic extensions that may surround as many as 50maturing T lymphocytes.

Secondary lymphoid organsAre specialized to trap antigen, to provide for initiation of the adaptive

immune response, and to provide signals for recirculating lymphocytes.

Lymph NodesAre a system of in line filters within the lymphatic vessel system.

Major regions: Capsule, Cortex with primary and secondary follicles,Medulla with medullary cords (extensions of inner cortex) and sinuses

Within the lymph node tissue, different cell types are clustered in differentregions.

The nodular cortical region contains an abundance of B lymphocytes.Nodules composed of resting (unstimulated) B lymphocytes are primary nodules.

Activated B lymphocytes form germinal centers and the nodules containing themare secondary nodules.


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Loosely scattered around the B lymphocyte rich nodules and in the sub- orPara- cortical region, are T lymphocytes, reticular cells (specialized fibroblasts),macrophages, and dendritic cells are also abundant here.In the medullary region, cells are in linear clusters called medullary cords. Themedullary cords are composed mostly of macrophages and activated, fully

differentiated, antibody secreting B lymphocytes called plasma cells.A system of loose lymphoid tissue called sinuses is arranged beneath theconnective tissue at the surface and then penetrates into the body of the lymphnode between the nodules and is more openly spaced in the medullary region.

This arrangement ensures the encounter of lymph borne pathogens withlymphocytes and other classes of leukocytes.

Lymph nodes filter lymph which from drains tissues.

Spleen

The spleen is a relatively large lymphoid organ in the abdominal cavityThe spleen: filters bloodis an important site of red blood cell destructionis an important site of white blood cell interaction,

lymphocyte activation and proliferationMajor regions: Capsule, Trabeculae, Parenchyma (Pulp; Red and

White)Spleen

Approximately of the total volume of the blood passes through thespleen in 24 hours.

The spleen responds to antigens that have reached blood circulation, andis an important antibody forming organ.

The spleen consists of areas rich in erythrocytes, the red pulp, and areas whereother blood cell types, including lymphocytes, are concentrated, the white pulp.

Within the red pulp, circulatory vessels open up into large diameter (for acapillary) winding vessels called sinusoids. The sinusoids are in between cordsof cells, the medullary cords. The medullary cords of the spleen can containmost of the various blood cell types.

The white pulp typically is arranged around a central arterial blood vessel.Immediately around the blood vessel are T lymphocytes in what is formally calledthe periarterial lymphatic sheath, PALS, and B lymphocytes are clustered innodules around this. At the periphery of the white pulp clusters is the marginalzone consisting of many blood sinuses and loose lymphoid tissue. The marginalzone contains an abundance of blood antigens and is a major site of the antigenand cellular interactions important in the immunological activities of the spleen.


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Lip and SkinSkin is composed of the Epidermis, consisting of epithelial tissue, and the

Dermis, consisting of an underlying connective tissueThick skin and thin skin can be distinguished by the thickness of the

epidermal layer

The epidermal-dermal junction is irregular and has papillae which areprojections of the dermisDistinguish the stratum basale and stratum corneum layers, note the

presence of hair in thin skin

TongueThe tongue is a mass of muscle covered by a mucous membrane.

Present on the upper surface are papillae of three primary types: filiform,fungiform, and circumvallate. The lateral borders of the circumvallate papillaebear taste buds and serous von Ebners glands.

Hand in your drawings before leaving lab today

Recommendations for the drawings:Label: Figure Number

Organ (Where appropriate)TissueCell TypeTotal MagnificationImportant Features

Blood: Draw the cell types that you did not draw previouslyDraw only the fully differentiated cell types

Vessels: Draw an artery and a veinLymph Node: Capsule, Cortex with primary and secondary follicles,

Medulla with medullary cordsSpleen: Capsule, Trabeculae, Parenchyma (Pulp; Red and White =

Lymphoid nodule)

histo lab #7 blood, lymphatics, skin

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