Unit 3: Connective Tissues

Transient cells

Can be thought as being involved with short term events such as a reaction to an injury or to an invasion by pathogens .1] They include macrophages, mast cells, plasma cells and cells that invade from the blood stream such as neutrophils, eosinophils, monocytes, and lymphocytes.

Fibrils are grouped into a ______ , and that is grouped into a _______ ________.

Fiber Collagen bundle

Ground substance is an amorphous, viscous gel. It is produced primarily by a connective tissue cell called the ________.

Fibroblast

The most common and largest type of GAGs. It binds to proteoglycan aggrecan. Creates large, hydrated spaces in the EM of cartilage.

Hyaluronic acid

The particular type of GAGs present in a particular c.t vary in occurrence and proportion. Some types of GAGs are:

Hyaluronic acid Sulfated Proteoglycans

Adipose tissue demonstrates two patterns of growth

Hyperplastic growth Hypertrophic growth

The result of _________ ________ growth is that both the size and the number of adipocytes can be influenced during the postnatal period but influences occurring later in life affect only cell size.

Hypertrophic growth

a class of GAG consisting of a sulfated glycosaminoglycan chain covalently bound to a core protein.

Sulfated proteoglycans

Type II Collagen

is found in cartilage and in certain tissues of the eye.

Type IV Collagen -

is found in the basement membrane.

Type III Collagen

is found in the c.t. components of the skin, G.I. tract, cardiovascular system, and uterus. *often found in association with reticular fibers.

Type V Collagen

is found primarily in fetal tissues although vestigial amounts remain in the adult.

plasma cells are particularly abundant in the _______ ________ of the G.I. tract and respiratory passageways. They are also found in the lymphoid organs.

lamina propria

Fibroblasts appearance may vary but overall they are ....

long, tapered cells with thin, flat nuclei.

________ connective tissues have a high cell content and a relatively low fiber content.

loose

Collagen is arranged into __________, and they are arranged into ______.

microfibrils fibrils

Mucus Connective Tissue

similar to mesenchymal connective tissue except that it contains collagen fibers and a more viscous ground substance.a] It develops from mesenchyme.

Structural proteins

serve to bind the c.t. cells to the surrounding collagen fibers of the matrix

_________ are specialized for the synthesis and storage of lipid. They may occur singly but more often in groups throughout loose connective tissues.

Adipocytes

White fat

Adipocytes are unilocular having the "signet ring conformation".

There are __ identified types of collagen

5

Macrophages

- long-lived, highly mobile, phagocytic cells found throughout the c.t.s of the body. - derived from the monocyte class of leucocyte which have migrated into the c.t. from circulation.

The Fibrous Component of the Matrix General comments

-Connective tissue fibers provide general support for other tissues. -In hollow organs and blood vessels which expand and contract c.t. fibers allow for flexibility. -Three types of fibers are found in c.t.s: collagen, reticular, and elastic fibers. -The density, proportion, arrangement, and occurrence of each type vary depending on the functional requirement of the tissue.

Fibronectin

-a cell matrix ligand since it promotes the attachment of c.t cells (especially fibroblasts) to collagen fibers. -directly influences the cytoskeletal organization of c.t. cells which can change their shapes and/or their functions.

Brown fat is a specialized type of adipose tissue. Capabilities include:

(a) It is thermogenic in that it can convert stored energy (in the lipid) into heat. (b) Brown fat is found in some mammal species (especially in hibernating species). (1) It is found in humans but only in the fetus and the neonate.

Plasma cells appearance

-basophilically staining fibroblasts being flat, tapered cells.a} -The nucleus is pinwheel shaped.

Elastic Fibers

-composed of the protein Elastin, which gives these fibers the ability to stretch. -found in most fibrous c.t. but are most abundant in those tissues requiring flexibility. 1] Ex; trachea, elastic arteries, skin, and uterus.

GAGs have several functions:

-contribute to the viscosity of ground substance. (barrier to the spread of pathogens following tissue injuries.) -provide structural support to c.t.s -act as a medium for the diffusion of nutrient and gases. -exert a direct influence on the surrounding cells. (for ex: development of cells.)

Mesenchymal Cells (aka; pericytes, perivascular cells)

-less widely distributed than are fibroblasts. -They are often found in association with blood vessels -are not very differentiated. -retain the multipolarity of embryonic mesenchyme cells which can develop into other c.t. cell types during gestation. -can develop into other cell types under the appropriate conditions.

Embryonic connective tissue

-mesenchymal -mucus

Collagen fibers

-most abundant and strongest of the three classes. -found in all types of c.t. in varying degrees. -has a tensile strength greater than does a similar sized strand of steel. (So it adds strength to the tissue and will decrease the effects of mechanical forces on the tissue.)

Dendritic cells

-present the antigen markers of pathogens to lymph nodes to mobilize humoral immunity. - also develop from monocytes.

Tropocollagen

-produced by the fibroblasts typically. - made by osteoblasts in bone and by chondroblasts in cartilage. -gets its strength from its structural arrangement.

Dense irregular connective tissue is found in areas such as:

-the sheaths of tendons and nerves, the capsules of organs, and the dermis. -areas subject to stress from a number of directions or that requires a protective barrier

Reticular Fibers

-thin collagen fibers arranged into delicate networks, not into bundles. -form a delicate supporting network around individual cells of many tissues and organs. -Ex; they constitute the inner stroma of lymphoid and hemopoietic organs. -also are a significant portion of the reticular lamina of the basement membrane.

The 5 types of specialized connective tissue

1) Cartilage 2) Bone 3) Dentin 4) Enamel 5) Blood

Mature connective tissues are classified based on:

1) relative density of fibers (i.e.: loose vs. dense c.t.s) 2) predominant cell type (ex; adipose tissue) 3) predominant fiber type if that is other than collagen (ex; elastic c.t.)

Components of Ground Substance

1) water 2) salts a] such as calcium phosphate 3) Glycosaminoglycans (GAGs)

Aereolar connective tissue

1] It is the most common type of loose c.t by far. 2] It is the class of c.t. supporting the epithelia. 3] It composes the stroma of various organs and glands. a} In certain organs and glands the areolar c.t. will also form septa which will divide the structure into lobes and/or lobules. 4] It makes up some of the superficial fascia and dermis.

Aereolar connective tissue functions

1] acts as a barrier to infection (up to a point) 2] cushions the body (up to a point) 3] allows for the passage of nerves, blood vessels, and lymph vessels

Adipose is found in a variety of places such as:

1] the hypodermis 2] surrounding and protecting certain organs 3] the medullary cavity of long bones

Reticular tissue is found in areas such as:

1] the inner stroma of many solid organs 2] the inner stroma of the lymphoid organs 3] the inner stroma of hemopoietic tissues such as red marrow

Four major classes of Sulfated proteoglycans

1} chondroitin sulfate 2} dermatin sulfate 3} keratin sulfate 4} heparin sulfate

White fat functions

1} stores energy 2} insulates the body form heat loss 3} cushions the body and protects delicate organs (ex; the kidney in mammals) from mechanical trauma

Macrophages move about by means of a special type of ameboid movement called ___________. This allows them to travel to the site of the infection.

Diapedesis.

Adipose Tissue.

Loose connective tissues having a high density of adipocytes

The ground substance and fibers are the extracellular components of the c.t. and make up the _____.

Matrix

___________ will give rise to all of the adult connective tissue.

Mesenchyme

In brown fat tissue the lipid is stored in several smaller vesicles. This pattern is termed __________.

Multilocular

Macrophages and mast cells can be differentiated by staining and, when present, by _____________ which are found only in macrophages.

Pseudopodia

Mesenchymal cells are similar in appearance to fibroblast but they can easily be distinguished by their _________ shape.

Stellate

Functions as a molecular sieve. It facilitates the diffusion of metabolites between the blood and the tissues. It acts as a physical barrier to prevent the spread of large particles such as bacteria and other pathogens.

The ground substance

mesenchymal connective tissue

fills the spaces between developing organs and is largely composed of mesenchymal cells and a fluid ground substance. -cells are stellate shaped and multipotent being able to give rise to all of the other connective tissue cell types.

Collagen is a protein polymer composed of monomeric units of the protein

Tropocollagen

The types of connective tissues are classified based on the relative proportions of three components:

ground substance, fibers, and cells.

A lymphocyte appears as

a cell having a prominent nucleus and little basophilic cytoplasm around it. (appear similarly in c.t. and in the blood stream)

It is very difficult to differentiate between B and T lymphocytes under

a light microscope

Regular Dense/ Dense Regular Connective Tissue

a.] this class of dense connective tissue has a regular, repeating pattern of fibers and very few cells. 1] Collagen also makes up the vast bulk, or often all, of the fibers. 2] Fibroblasts and fibrocytes also are the most common cell types. b] is characterized by having a great resistance to mechanical forces. 1] The parallel arrangement of it's fibers gives a great deal of strength in one direction.-->in tissues such as tendons and ligaments.

Reticular connective tissue

a] Reticular is a loose c.t. where reticular fibers are the predominant fiber type. 1] The reticular fibers form a delicate, supportive, framework. 2] Associated with these reticular fibers are Reticular Cells/Reticulocytes which maintain the fibers and can also perform

Irregular Dense/ Dense Irregular Connective Tissue

a] This class of dense connective tissue has a random weave of fibers and very few cells. 1] Collagen makes up the vast bulk, or often all, of the fibers. 2] Fibroblasts and fibrocytes are the most common cell types.

Elastic connective tissue

a] dense connective tissue where the predominant fiber type is the elastic fiber. b] It is found in areas that must be able to deal with a high degree of mechanical stress but also be highly resilient. 1] Ex; elastic cartilage and elastic arteries.

Hyperplastic Growth

adipocyte precursors proliferate for a limited period postnatally.

The size of adipose tissue reflects the number of ________ present and their size.

adipocytes

Mesenchymal cells can develop into a variety of c.t. cell types including

adipocytes and mast cells, and can even develop into smooth muscle cells.

Plasma cells are actually _______ secreting B lymphocytes, and are widely dispersed throughout connective tissues.

antibody

Laminin

associated with the basement membrane where it is a specific attachment protein for epithelial cells to the type IV collagen of the basement membrane.

Brown fat

a} Adipocytes are multilocular. b} This is thermogenic adipose tissue and is found only in placental mammals.

The cytoplasmic granules of the macrophage contain a variety of substances:

a} Some contain digestive enzymes to facilitate phagocytosis. 1} These include lysosomes. b} Some produce immunoregulatory substances as well as a vast array of unrelated substances such as interferon, lysozyme, prostaglandins, peroxide, and a variety of growth factors.

Mast cells involvement in the immune response

a} histamine to increase vascular permeability b} eosinophil chemotaxic factor to attract eosinophils which will phagocytosize certain pathogens and trigger the reverse of the inflammation response. c} prostaglandins to increase edema d} heparin which serves as an anticoagulant e} and a number of enzymes which degrade various c.t. components.

Dense connective tissue

have a high fiber content and a relatively low cell content.

Connective tissues are a diverse class of tissues including:

bone blood cartilage adipose areolar (AABBC)

Special connective tissue

c.t. which are most modified from the mesenchymal format. Four of the five are mineralized tissues

Permanent cells

can be thought of as being involved with the long term maintenance of the c.t.1] They include: mesenchymal cell, fibroblasts, and adipocytes.

Fibronectin also plays a role in other cell processes such as:

cell migration cell differentiation phagocytosis chemotaxis.

Hypertrophic Growth

change in the size of adipocytes due to lipid accumulation. -growth, and it's reversal, can occur throughout an individual's lifetime.

The three classes of connective tissue fibers

collagen fibers reticular fibers elastic fibers

Macrophages are similar in appearance to mast cells in that they both possess prominent __________ _________.

cytoplasmic granules

hyaluronic rich matrix is especially suitable for cell migration and proliferation. It may also prevent precocious ___________

differentiation

Fibroblasts are derived from ________ _________. (as are most c.t. cells).

embryonic mesenchyme

Lymphocytes will commonly penetrate the __________ to perform their functions.

epithelium

The cell types and their relative densities are highly variable and depend largely on:

fiber density, location, and functional state.

-immature c.t. cells which will mature into fibrocytes -responsible for producing at least some of the organic component of the matrix. -often found in association with collagen bundles. -they produce all three fiber types as well as the ground substance.

fibroblasts

-mature fibroblasts. -may help to maintain the c.t. by aiding in it's repair. -similar in appearance to fibroblasts but they have fewer cytoplasmic granules.

fibrocytes

Adipocytes will alternately store fat and become depleted. Lipid deposition and mobilization is controlled by ___________ secretions and by the organism's nutritional state.

neuroendocrine

In ____________ there is contact with the external environment and so a greater need for protection of the underlying tissues by lymphocytes from pathogenic invasion.

passageways

The cells of the c.t. proper can be divided into two groups:

permanent and transient cells.

Mast Cells

play a role in the inflammation reaction and produce a variety of chemicals which promote it

Osteonectin

promotes the attachment of bone cells to collagen.

Chondronectin

promotes the attachment of cartilage cells to collagen.

Specific interactions between the surface receptors of cells and GAGs may play a role in the _______ of cellular functions.

regulation

Type I collagen

s the most abundant and widespread type.

Lamina Propria

specialized loose c.t.s of the alimentary canal and respiratory tract

Plasma cells are rarely found in

the blood

White fibers

the major structural protein in the human body. Protein fibers formed by collagen molecules.

Mucus connective tissue is typified by Wharton's Jelly of the mammalian ___________

umbilicus

In white fat tissue the lipid is stored in a single, large droplet described as ___________. This gives the adipocyte it's classic "signet ring" appearance when full.

unilocular