Connective tissue and fat tissue
Natalia Łysiak
Connective tissue
Connective tissue
The connective tissue 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.
Ground substance
Ground substance
- Clear, colorless, viscous fluid that fills the space between the cells and fibers.
- It is composed of proteoglycans, glycosaminoglycans and glycoproteins and that allow the connective tissue to act as glue for the cells to attach to the matrix.
- Its functions as a molecular sieve for substances to travel between blood capillaries and cells.
Fibers
Fibers
They are long, slender protein polymers present in different proportions in different types of connective tissue. There are:
- Collagen: very strong and provide flexibility and consisting of many closely packed tropocollagen fibrils.
- Elastic fibers: composed of microfibrils of elastin and fibrillin embedded in amorphous elastin, they are very stretchy and assume their original shape after being stretched.
- Reticular fibers: very thin and provide support for many soft organs and blood vessels. They have high carbohydrate content.
Ground substance and fibers form the matrix.
The matrix can be fluid, semifluid, gelatinous, or ground substance and protein fibers.
It provides a medium for the transfer of nutrients and waste materials between connective tissue cells and the bloodstream.
Embryonic connective tissue
Embryonic connective tissue
- MUCOUS TISSUE: loose connective tissue that is the main constituent of the umbilical cord. It consists of a jelly-like matrix with some collagen fibers in which large stellate-shaped fibroblasts are embedded.
- MESENCHYMAL TISSUE: consists of a gel-like amorphous matrix containing only a few scattered reticular fibers. It's only found in embryos.
Connective tissue proper
Connective tissue proper
The cells that mostly compose this type of tissue are called fibroblasts which often have an oval nucleus with two or more nucleoli.
Loose connective tissue
Loose connective tissue
- Most abundant form of collagenous connective tissue.
- It occurs in small, elongated bundles separated by regions that contain ground substance.
- For example adipose tissue or areoral tissue which is wildly distributed and serve as a universal packing material between other tissues.
Dense connective tissue
- It has thicker, denser fibers and fewer cells.
- The matrix is made up mostly of collagen fibers, with fibroblasts arranged in rows.
- This type of connective attach muscle to bone and bone to bone, respectively.
- Important to have strong connections between muscle and bone for our body to move properly.
Dense connective tissue
Dense regular connective tissue
Regular
- Consists of closely packed bundles of collagen fibers running in the same direction.
- These collagen fibers are slightly wavy and can stretch a little bit.
- This tissue forms tendons, aponeurosis and ligaments. It also forms the fascia, which is a fibrous membrane that wraps around the muscles, blood vessels, and nerves.
Dense Irregular Connective tissue
Irregular
- In which the bundles of collagen fibers are much thicker and arranged irregularly.
- This tissue is found in areas where tension is exerted from many different directions.
- It is part of the skin dermis area and in the joint capsules of the limbs.
Elastic connective tissue
- It' formed mostly by elastic fibers arranged in bundles.
- It's present in those organs and those structures which require a spread followed by a return to the initial size.
- Examples are lungs, walls of arteries and vocal cords.
Elastic connective tissue
Reticular connective tissue
- The only fibers in its matrix are the reticular fibers, which form a delicate network.
- The reticular tissue is limited to certain sites in the body, such as internal frameworks that can support lymph nodes, spleen, and bone marrow.
Reticular connective tissue
Special connective tissue
Special connective tissue
Divided into:
- Adipose tissue or fat tissue
- Cartilage
- Bones
- Blood
Cartilage
Cartilage
- It's a flexible tissue and it's strong due to the collagen fibers within its matrix, and it is resilient due to a gel matrix. Cartilage is also found in the body as a cushion within the skeletal system.
- Composed of specialized cells called chondroblasts and it doesn't contain blood vessels.
- It includes the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes, and the intervertebral discs.
Bones
Bones
- Bones are made up of different types of connective tissue, including bone tissue and marrow. Bone tissue is either spongy or compact depending on the organization of the cells and matrix.
- It is mostly formed of calcium phosphate in the chemical arrangement termed calcium hydroxyapatite, which gives bones their rigidity.
Blood
Blood
- It is an atypical connective tissue since it does not bind, connect, or network with any body cells. It is made up of blood cells and is surrounded by a nonliving fluid called plasma.
- Its major functions are delivering necessary substances, such as nutrients and oxygen, to the cells and transports metabolic waste products away from those same cells.
Adipose tissue
Adipose tissue
- It's a loose connective tissue, composed of adipose cells, so called adipocytes.
- Other types of cells that comprise adipose tissue include fibroblasts, white blood cells, nerves, and endothelial cells.
Functions
Adipose tissue functions as a cushion against trauma for the tissues of the body. Many of the major organs are wrapped in a layer of visceral fat, deep inside, to protect the organs during physical trauma and to insulate the body from heat loss.
Adipose tissue is found directly beneath the skin, between muscles, around the kidneys and heart, behind the eyeballs, and abdominal membranes.
Infants and young children will have a continuous layer of adipose tissue for protection while learning to be mobile that will thin as they grow into adolescence.
The layer gives their body that round, plump appearance.
Another function of adipose cells is to increase the body's sensitivity to insulin, thereby protecting against obesity. This help to reduce body weight and reduce the risk of developing conditions such as diabetes and cardiovascular disease.
Adipocytes
Adipocytes
They contain droplets of stored fat, triglycerides, that can be used for energy.
These cells swell or shrink depending on whether fat is being stored or used.
Over time, if the body does not use the material for fuel, it will be stored in the cell on a long-term basis. The more storage, the larger the cell becomes. So no new cells are created nor old cells are destroyed.
Carbohydrates and proteins can also be converted into storage forms if they are not used immediately, contributing to the growth of the cell.
White adipose tissue (WAT)
WAT
- Synthesize the enzyme lipoprotein lipase which is transferred to the capillary endothelium and it hydrolyzes dietary fat into fatty acids and glycerol.
- Lipid storage is stimulated by insulin, which increases the rate of synthesis of lipoprotein lipase.
- Release of lipids is affected by neural impulses and/or adrenaline.
- Their function is to store energy.
Brown adipose tissue (BAT)
- Brown fat cells are smaller in size and quantity and derive their color from the high concentration of mitochondria for energy production and vascularization of the tissue.
- The lipid in brown fat is burned to provide high levels of energy as heat in animals who hibernate and infants who may need additional thermal protection
BAT
Endocrine system
Endocrine system
- Adipose tissue also produces endocrine hormones which regulate adipocyte activity and influence metabolic activity in other organ systems.
- For example sex hormone metabolism, blood pressure regulation, insulin sensitivity, fat storage and use, blood clotting and cell signaling.
BIBLIOGRAFY
- https://www.thoughtco.com/adipose-tissue-373191
- http://study.com/academy/lesson/adipose-tissue-function-location-definition.html
- https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0022672/
- https://courses.lumenlearning.com/boundless-ap/chapter/connective-tissue/
- http://study.com/academy/lesson/connective-tissue-types-functions-disorders.html
- Cell Biology and Histology, L. P. Gartner
- Area scientifica e farmaceutica, Editest
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