Human Tissue Types II: Connective Tissue Quiz

Answer: Matrix

The matrix is the substance that exists between the cells in the connective tissue. The main constituents of the matrix are fibers, and ground substance, which is the material existing between the cells and fibers.

In contrast to epithelial tissues, connective tissues normally do not cover surfaces (although areolar connective tissue is an exception: it lines joint cavities). Instead, connective tissues have a wide variety of functions, including support (e.g. the skeleton), energy reserves (e.g. fat), and in nutrition (e.g. blood).

Answer: False

It is actually the other way around. The suffix "-blast" means "to bud" or "to sprout". The blasts actually produce the matrix, and matures into cytes when the matrix is sufficient. They retain the ability for cell division.

Cytes, on the other hand, have a much reduced capacity for cell division. Their main role is to maintain the matrix.

From the question: Osteoblasts and osteocytes are cells found in bone.

Answer: Mediating allergic reactions

Mast cells are large, and have a granulated cytoplasm. They are important in allergic reactions; they secrete histamine, which dilates small blood vessels in an immune response. This allows blood to reach the site of damage, and causes the redness seen with inflammation. You may have heard of anti-histamines being used to treat allergies, especially hay fever; these help to decrease the response of mast cells. Mast cells also release heparin, which is thought to defend against invading pathogens such as bacteria.

Connective tissues also contain fibroblasts/-cytes, adipocytes, and macrophages.

Answer: Muscle fibers

Muscle is in fact another tissue type altogether, which will be covered in the next quiz of the series: Human Tissue Types III.

Collagen fibers are very strong but flexible fibers that make up around 30% of your dry body weight! There are different types of collagen (at least 15), which can each confer different properties to the tissue it is present in. For example, cartilage contains Type II collagen, which is particularly good at retaining water, which makes cartilage quite spongy compared to bone.

Reticular fibers are found primarily in the spleen, liver, and lymph nodes. They also contain collagen protein (mainly Type III) as collagen fibers do. They provide a more delicate branched network, and provide support and strength to the tissue. They also help to form the basement membrane, which underlies epithelia.

Elastic fibers contain elastin as the main protein, and their main property is that of stretching - they can stretch up to about 1.5 times their length. They form irregular branched networks, and are found primarily in the lung and aorta.

Answer: GAG

Glycosaminoglycans are polysaccharides that trap water, forming hydrated gels. Most exist as proteoglycans, which means they are associated with proteins. The proteins form a spine, and the GAGs project from the spine like bristles of a brush - this conformation is very good at holding water. GAGs include chondroitin sulfate (found in cartilage and bone) and dermatan sulfate (found in skin, tendons, and blood vessels).

As well as making the connective tissue more spongy, GAGs provide strength under compression.

Answer: Marfan's syndrome

Marfan's syndrome is inherited from generation to generation, and is caused by a mutation in the gene for the protein fibrillin, found in elastic fibers. Tissues that have abundant elastic fibers are thus affected; these include the covering layer of bone (periosteum), the ligament that supports the lens in the eye, and the walls of arteries. Symptoms can therefore include blurred vision (due to the displacement of the lens) and, more seriously, the aorta can weaken, which can lead to sudden bursting and subsequent death.

Answer: Tendons and ligaments

In dense regular tissues there is very little ground substance and few cells (generally fibrocytes are present). There are many fibers (mainly collagen) arranged in regular, parallel bundles, which gives a high tensile strength to the tissue - the tissue can withstand pulling along the axis of the fibers. This tissue is normally silvery white.

Dense irregular tissue also has little ground substance and high proportions of fibers. However, here the bundles are in all directions, and this means that stress can be loaded on the tissue in a non-specific direction. Examples of where it is found are in the periosteum and perichondrium.

Finally, loose connective tissue is mostly made up of ground substance, and has a high water content. It has relatively few fibers, but has some cells. This can be found in blood vessels and nerves.

Answer: External ear

Hyaline cartilage is the most abundant type of cartilage, and is found in various places, such as covering bone ends in synovial joints, trachea, bronchi, and the nose. It appears as a shiny, blue-white substance. It contains fine collagen fibers, and has many chondrocytes situated in spaces named lacunae (which means "little lakes"). Usually it is surrounded by a perichondrium.

Elastic cartilage contains a network of elastic fibers in which the chondrocytes are located. It provides strength, elasticity, and gives the shape of the ear. Try to fold your ear over itself and let go - it will ping back like an elastic band!

Answer: Havers

Clopton Havers was a physician in the 17th century, and he undertook pioneering research on the microstructure of bone. The structures in the question are called Haversian canals (also Haversian systems or osteon). These are made up of a central canal, which contains a blood vessel.

The vessel is surrounded by rings of bone called lamellae. There are osteoblasts and osteocytes present between the lamellae to maintain the Haversian canal. The osteocytes connect to each other through the lamellae via projections called canaliculi.

Answer: False

This is false. Actually, osteoarthritis affects men and women in equal numbers. It is a common type of arthritis and is degenerative, resulting in the wearing away of joints, especially the hip and knee. It can develop early, for example as the result of a sports injury.

Symptoms include pain and stiffness in the joints, and is caused by the wearing away of the cartilage in the joint; the exposed bone becomes thickened (sclerotic) and shiny (eburnated). Also, cysts can develop in the bone, and bony projections called osteophytes can occur. These osteophytes can frequently be seen on the distal phalanges. They are then called Heberden's nodes and are more commonly seen in women.