Chapter 9(connective Tissue) Flashcards
Connective tissue arises from
widely scattered free mesenchyme cells and is correspondingly ubiquitous in its distribution.
What is the function of Connective tissues?
bind structures together, form a framework and support for organs and the body as a whole, store fat, transport substances, protect against disease, and help repair tissue damage.
Connective tissues are characterized by
an abundance of intercellular matrix with relatively few cells.
Connective tissue is made up
of cells, ground substance and fibres.
what is the matrix?
The ground substance and the fibres together
Connective tissues ate different from epithelial tissues in that
its cells are not joined to form sheets.
_____ serves as a connecting system binding all other tissues together.
connective tissue
___ connect the skin to underlying tissues
- fascia
adipose tissue provides ______ from the skin.
insulation against heat losses
What is is responsible for the production of blood cells.
haemopoietic tissue,
connective tissue cells can be differentiated from one another by their___
varying amounts of extracellular matrix.
What tissue is particularly susceptible to shrinkage during fixation and why?
- Connective
- because of its mixed
composition of cells, fibres and matrix,
Connective tissue cells are usually divided into two groups based on their ability to move within the connective tissue namely
- Fibrocytes (or fibroblasts) and fat cells are fixed cells.
- Macrophages, monocytes, lymphocytes, plasma cells, eosinophils and mast cells are wandering cells.
What is the Most common cell type in connective tissue.
Fibrocytes
What is Considered the “true” connective tissue cell?
Fibrocytes
Which organelle is the main visible feature of fibrocytes in microscopy?
Flattened nuclei
______ connecting tissue cell lacks many organelles, indicating low activity
Fibrocytes
when does the Fibrocytes become active?
When Stimulated by tissue damage or other signals.
What is the active state of Fibrocytes called?
Fibroblasts
What are the components of the Fibroblasts?
Large, flat, and branching with a single oval nucleus.
Function of the fibroblast
Synthesize and secrete proteins (mainly collagen) to build and repair connective tissue.
What is the main function of adipocytes?
primary role is storing lipids, mainly as triglycerides.
What happens to the adipocytes When well-fed?
the cell cytoplasm becomes a thin rim around a single, massive lipid droplet, pushing the flattened nucleus to the edge.
the diameter of an adipocyte is
up to 100 micro meter
What happens to a “starving” adipocyte ?
may contain multiple small lipid droplets and gradually comes to resemble a fibrocyte.
Fat storage and mobilization are tightly controlled by:
- Nerves: Sympathetic nervous system plays a key role in mobilizing stored fat.
- Hormones: Insulin promotes fat storage, while glucagon and other hormones signal release.
Adipocytes secrete:
the protein leptin,
Function of protein leptin
signals the brain’s appetite centers about fat reserves.
Leptin deficiency can lead to
obesity in animal models
The total number of adipocytes is primarily determined by
the preadipocytes (or lipoblasts) generated during fetal and early postnatal development.
What are Reticular cells ?
These are specialized “fibrocytes” that build a supportive network of fibers within lymphoid organs, enabling proper organization and function of immune cells.
Function of reticular cells
- Forming a network of reticular fibers
- Providing support and organization
Fibrocytes posses nucleus which are _____ on the microscope
Large and slightly stained
Macrophages originate from precursor cells called
monocytes.
Monocytes develop in the
bone marrow and circulate in the bloodstream.
What are macrophages?
Macrophages are large cells with blunt cytoplasmic processes (extensions), small round nuclei (one per cell), and the ability to engulf and destroy foreign bodies (phagocytic).
In resting state, macrophages have ____
processes and are less mobile.
What happened during inflammation (active stage) in macrophages?
they retract their processes and become more amoeboid (able to change shape and crawl) for increased mobility.
What are mast cells?
Mast cells are plump cells with smaller nuclei and granular cytoplasm.
Function of mast cells
Present even in healthy tissues, constantly monitoring for potential threats.
How does mast cells response to potential threats?
they discharge the contents of their vesicles upon encountering antigens (foreign substances like bacteria or pollen),
What are the vesicles found in mast cells and their function?
- Heparin: They increase blood flow in close by vessels
- histamine vesicles: They increase the permeability of the vessel walls to plasma constituents and other white blood cells.
Description of Lymphocytes?
Smaller than average cells (6-8 μm) with a dark-staining, round nucleus. The cytoplasm forms a thin rim around the nucleus, making them inconspicuous in microscopy.
Lymphocytes are Primarily found in ?
connective tissue beneath the digestive tract epithelium
What happens when lymphocytes are triggered by immune reaction?
Some lymphocytes differentiate into specialized cells called plasma cells
Function of the plasma
producing antibodies, protein molecules that target and neutralize specific pathogens.
What are the changes that occur when monocytes differentiate into plasma
their cytoplasm expands significantly, and they become basophilic (staining blue with certain dyes). The nucleus has a distinctive “cartwheel” appearance due to the radial arrangement of chromatin material.
Plasma are located at;
the digestive tract tissues and lymphoid organs
Where does Eosinophilic Cells Develop?
in the bone marrow, similar to monocytes.
Description of Eosinophilic Cells
Large, round or oval cells with abundant bright red granules in their cytoplasm.
What is the Function of Eosinophilic Cells?
Enter inflamed tissues early on, phagocytosing (engulfing) immune complexes (antigens bound to antibodies).
What is a Epitheloid Cell?
When monocytes transform into macrophages and then arrange themselves in tightly packed sheets in chronic inflammation.
What gives rise to the cell types of the connective tissue?
Mesenchymal cells
Function of the mesenchymal cells
They may regenerate blood vessels or smooth muscle which have been lost as a consequence of tissue damage.
What are fibres
These are long thread-like products formed probably by the activities of the fibroblasts.
The three kinds of fibres are ?
collagenous or white, elastic or yellow and reticular .
What are the dominant fibre type in most connective tissues?
Collagen fibre
Which type of fibres are not elastic and resist stretching, maintaining tissue integrity under tension.
Collagen
Collagen fiber structure hierarchy includes
Bundles, Fibrils, Microfibrils, tropocollagen
There are how many known types of tropocollagen?
21
What type of collagen fibre plays a crucial role in the structure of the basal lamin
Type IV
What type of fibre are the backbone of connective tissues, offering remarkable strength and support.
Collagen fibers
Collagen fibre types differ in their content of
the amino acids hydroxyproline and
hydroxylysine and amount of carbohydrates attached to the collagen molecules.
What are the major fibre-forming tropocollagens.
Types I, Il and Ill
Microscopic observation of elastic fibre requires special stains like
resorcin fuchsin to highlight their presence, as they lack visible substructure under simple light microscopy.
Which types of fibre are light yellow?
Elastic fibre
Resorcin fuchsin is one of these stains, which gives the elastic fibres a ____ colour.
dark violet
Elastic fibre is composed of ____ embedded within ____.
- Microfibrils
- an amorphous matrix
Matrix Makes up how any percent of the fiber?
90%
Matrix composed of ___ protein.
elastin
Elastic fibres can be stretched by about how many percentage of their original length?
50%
Elastin molecules are interconnected by
unique desmosin and isodesmosin bonds
Distribution of elastic fibers and their function
Ligaments: Providing flexibility and recoil for joint movement.
Blood vessels: Enabling vessel expansion and contraction during blood flow.
Areolar connective tissue: Found in smaller amounts, contributing to tissue elasticity.
What are Reticular fibers? .
These are thin, delicate collagen fibers supporting individual cells within tissues
the main type of tropocollagen found in reticular fibres are?
The type Ill,
Function of the Reticular fibres:
give support to individual cells, for example, in muscle and adipose
tissue.
Reticular fibre occur abundantly in
glands and lymphatic organs.
What is are ground tissues?
material within which all other connective tissue elements are embedded.
the ground substance consists mainly of water whose major role is
to provide a route for communication and transport (by diffusion) between tissues.
water in ground substance are stabilized by
a complex of glycosaminoglycans
(GAGs), proteoglycans, and glycoproteins
Where is Ground substance found?
all cavities and clefts between the fibers and cells of connective tissues.
What is the main structural constituent of ground substance?
proteoglycans.
What is responsible for the highly viscous character of the ground substance?
Proteoglycans
Proteoglycans consist of
proteins (~5%) and polysaccharide chains (~95%) which are covalently linked to each other
What is the dominant glycosaminoglycan in connective tissues.
Hyaluronan (or hyaluronic acid)
What are the five glycosaminoglycan ?
Hyaluronan, chondroitin sulfate, dermatan sulfate, keratan sulfate, and heparan sulfate
_____ serves as a “backbone” for the assembly of other glycosaminoglycans in connective and skeletal tissue,
Hyaluronan
What is a domain in ground substance?
roughly spherical space with a diameter of around 0.5 micrometers, formed by the coiled arrangement of hyaluronan and other attached glycosaminoglycans (GAGs
The restricted motility of larger molecules in the domain inhibits
the spread of microorganisms through the extracellular space
invasive bacteria determined to go through the domain mesh produce the enzyme _____
hyaluronidase, which depolymerises hyaluronic acid.
The components of the ground substance, are synthesized by
cells of the connective tissues, the fibrocytes.
Connective tissue can be classified into three categories:
proper, embryonic, and specialized.
What is a proper connective tissue ?
A generalized form of connective tissue which contains all of the basic components of connective tissue in reasonable proportion,
Ordinary Connective Tissue can be classified into
- Loose fibroelastic areolar connective tissue:
- Loose fibroelastic adipose connective tissue
What is the most common type of connective tissue ?
Loose fibroelastic areolar connective tissue
Loose fibroelastic areolar connective tissue is found
under the epidermis of the skin, in the wall of the alimentary canal and blood vessels, and in the solid organs and muscle blocks
Function of Loose fibroelastic areolar connective tissue?
It holds organs and epithelia in place, and has a variety of proteinaceous fibers, including collagen and elastin.
loose connective tissue lacks
massive fibrous reinforcement.
The _____ is the same both loose and dense connective tissue.
intrinsic strength of collagen
What is an Adipose tissue?
This is a special kind of areolar connective tissue which is dominated by fat cells, or adipocytes
Adipose cells are probably modified
fibroblast cells.
Adipose tissue are found at the
epidermis of the skin, around the kidneys and other abdominal organs, in bone marrow and in the membranes of the joints.
A brownish type of adipose tissue is found in
hibernating mammals
Function and of the adipose tissue
During starvation, this stored fat is utilised for supplying the necessary energy.
What are Dense connective tissues
Tissues high density of extracellular ‘ fibers, and relatively smaller proportions of ground substance and cells.
Dense connective tissue can be classified based on the type of fibre as
- Dense collagenous connective tissue
- Dense elastic connective tissue
- Dense reticular connective tissue
Dense collagenous connective tissue is
found
wherever the tensile strength of collagen is of paramount importance. dermis (the layer of the skin which yields leather), tendons and ligaments, and organ sheaths (such as the sclera, or “white” of the eye).
Dense elastic connective tissue is found
wherever the elasticity of elastin is of paramount importance,as in the
ligamentum flavum (flavum refers to the yellow color conferred by the elastin) and the aorta.
Dense fibroelastic connective tissue may be further described as ______depending on the orientation of the fibers.
either regular or irregular,
What is irregular connective tissue?
It is areolar tissue with greater proportion of collagenous fibres arranged irregularly to form a thick pad.
Where is irregular connective tissue found?
in the dermis of the skin, in the membranes around bones and cartilage and in the capsules of spleen, testis etc.
What is regular connective tissue?
collagenous fibres are regular parallel bundles as in tendons, ligaments and aponeuroses.
What are Tendons?
These are bundles of collagenous fibres with fibroblast (tendon cells) between them.
Fibröblasts appear _____in cross-section and_____ in longitudinal section of tendons.
- stellate (star-shaped)
- columnar
The fibres and cells of tendons are grouped into small bundles surrounded by a thin layer of areolar tissue called ?
the endotendineun.
The primary bundles of tendons are
again covered by areolar tissue to form bigger bundle called ?
the peritendineum-
the entire tendon is covered by ____
epitendineum,
Nerves and blood vessels do not enter what part of the tendon
the primary bundles.
What are Aponeuroses.
These are flat tendon-like sheets with layers of fibres and cells which join the fibres of another layer.
Aponeurosis attaches
a flat muscle to
another flat muscle or to a flat bone.
Ligaments attach
bone to bone.
Tendons attach
muscle to bones.
Neighbouring domains overlap and form
a more or less continuous three-dimensional molecular sieve in the interstitial spaces of the connective tissues.
Dense Fibrocollagenous (or just fibrous) tissue contains _____ proportion of collagen.
a substantial
What is the principal feature of dense fibrous tissue
flexibility combined with great tensile strength.
Elastic tissue is a dense connective tissue which contains
predominantly elastic fibers rather than collagen.
Example of fibrous tissue include
The sclera of the eyes
_______ tissue is found as the main framework of lymphatic organs, like spleen, lymph nodes, thymus etc. and also in bone marrow.
Reticular connective tissue
Description of the fibres of reticular tissues
very thin and are argyophilic, i.e., stains with silver nitrate.
Embryonic connective tissues
- Mesenchymal connective tissue
- Mucous connective tissue
Functions of Connective Tissue
- transport of nutrients and metabolites
- immunological defense
- mechanical support
- tissue repair
- reserve energy storage
- heat generation
- haemopoiesis
Function of Macrophages
Macrophages remove and digest the byproducts of both bacterial warfare and normal growth and degeneration.
What are Function of the Monocytes?
differentiate into macrophages when they enter connective tissue.
Function of lymphocytes
They possess in their secretory product and on their cell membranes the ability to recognize and bind to foreign substances.
neutrophilic granulocytes; the name derives from
the staining properties, neither acidophilic nor basophilic, of these cells
specific granules).
Function of the Neutrophils
Neutrophils have the ability to approach, engulf, and kill most bacteria.
Function of Eosinophils
Eosinophils are involved in responses to allergy and parasites.
Function of basophils
Basophils are the circulating equivalent of tissue mast cells.
The major determinant of the mechanical properties of most connective tissue is
the extracellular matrix which is secreted by the cells within it
Function of the ground substance of ordinary connective tissue:
serves mainly to prevent extracellular water from pooling in the lowest part of your body.
What is the major structural feature in special forms such as cartilage and bone.
ground substance
What forms the main structural elements?
extracellular fibres
___ offers flexibility with high tensile strength.
Collagen
Densely packed collagen fibers provide
strength with resistance to tearing and stretching.
Loosely packed collagen fibers provides
free movement within definite limits.
Function of Reticular fibers
provide a delicate supporting framework for individual cells, especially when such cells accumulate en masse to form a large solid organ such as the spleen lor the liver.
Function of Elastin:
helping restore normal shape after distortion.
dense elastic fiber concentrations provides
strong elastic properties
lesser concentration of collagen prevent
over-stretching under severe stress.
________ exceed all other cell types for calories stored per cell.
adipocytes
______ manufactures the fibers and ground substance of connective tissue.
Fibroblast
Function of brown fat
responsible for generating heat
What is another name for brown fat ?
Multiocular fat
What is a connective tissue disease ?
any disease that has the connective tissues of the body as a primary target pathology.
What is autoimmunity?
inflammation in tissues as a result of immune system that is directed against
one’s own body tissues
What is Marfan syndrome
a genetic disease causing abnormal fibrillin.
What is Scurvy
A disease caused by a dietary deficiency in vitamin C, leading to abnormal collagen.
What is Ehlers-Danlos syndrome -
deficient type Ill collagen- a genetic disease causing progressive deterioration of collagens, with different
EDS affecting different sites in the body, such as joints, heart valves, organ walls, arterial walls,
What is Loeys-Dietz syndrome
A disease related a genetic with an to Marfan syndrome, emphasis on vascular deterioration.
What is Pseudoxanthona elasticum
an autosomal recessive hereditary disease, caused by calcification and fragmentation of elastic fibres, affecting the skin, the eyes and the cardiovascular system.
What is Systemic lupus erythematosus
a chronic multisystem, disorder of inflammatory probable autoimmune etiology, occurring predominantly in young women.
What is Fibrodysplasia ossificans progressiva -
disease of the connective tissue, caused by a defective gene which turns connective tissue into bone.
What is Spontaneous pneumothorax ?
collapsed lung, believed to be related to subtle abnormalities in connective tissue.
What’s Sarcoma
a neoplastic process originating within connective tissue.
What is Osteogenesis imperfecta
Brittles bone disease caused by insufficient production of good quality collagen to produce healthy, strong bones.
