Test: Connective Tissue - 3 - NEET MCQ

• Histiocytes destroy bacteria by phagocytosis.
• A histiocyte is an animal cell that is part of the mononuclear phagocyte system also known as the reticuloendothelial system or lymphoreticular system.
• The mononuclear phagocytic system is part of the organism's immune system. The histiocyte is a tissue macrophage or a dendritic cell.

Mononuclear Phagocyte System:

Scavenger cells of alveoli are called dust cells.

• These are the alveolar macrophages, reside on the internal surface of air cavities of alveoli, alveolar duct, and bronchioles.
• They are the mobile scavengers that serve to engulf foreign particles in the lungs such as dust, bacteria, carbon particles, and blood cells from injuries.

• A plasma cell is a modified B-lymphocyte of blood. They are transported by the blood plasma and the lymphatic system.
• Plasma cells originate in the bone marrow; B cells differentiate into plasma cells that produce antibody molecules closely modeled after the receptors of the precursor B cell.
• Once released into the blood and lymph, these antibody molecules bind to the target antigen and initiate its neutralization or destruction.

A mast cell (also known as a mastocyte or a labrocyte) is a migrant cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a part of the immune and neuroimmune systems

• Mesenchyme is a type of connective tissue found mostly during the embryonic development of bilateral animals (triploblastic). 
• It is composed mainly of ground substances with few cells or fibers.
• It can also refer to a group of mucoproteins resembling mucus found.
  Example: In certain types of cysts.
• It is most easily found as a component of Wharton's jelly.

• Glia, also called glial cells or neuroglia, are non-neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system that do not produce electrical impulses.
• Glia was discovered in 1856, by the pathologist Rudolf Virchow in his search for a "connective tissue" in the brain.

• Yellow fibres are made up of elastin protein, they are thinner, less numerous and branched and are pale yellow in colour. They are very elastic and remain stretched due to tension in areolar tissue. 
• White fibres are made up of collagen protein. They are the most abundant fibrous elements of areolar and other connective tissues. They are long, unbranched fibres of a soluble and shining collagen protein.
• Reticular fibres are made up of reticulin protein. They are delicate, freely branching and inelastic fibres found interwoven to form networks.

Yellows and white fibres occur as singly and bundle respectively.

• The yellow fibres are thicker and fewer than white fibres. They are straight and occur singly. They are flexible, elastic and branched.
• White fibres on the other hand occur in bundles, called fascia and are formed of collagen.

Cartilage is composed of specialized cells called chondrocytes that produce a large amount of collagenous extracellular matrix, the abundant ground substance that is rich in proteoglycan and elastin fibers.

Cartilage is classified into three types: Elastic Cartilage, Hyaline Cartilage, and Fibrocartilage.
They differ in relative amounts of collagen and proteoglycan.

Cartilage is avascular i.e. no vessels to carry blood to cartilage tissue.
This lack of blood supply causes cartilage to heal very slowly compared with bones.
Nutrition supplied to the cartilage cells: Chondrocytes by diffusion.

• Hyaline Cartilage is semi-transparent cartilage and is extremely strong but very flexible and elastic.
• It is located on many of the joint surfaces. It is pearly bluish in color with firm consistency and has a large amount of collagen.
• Externally, it is covered by a fibrous membrane, called the perichondrium, except at the articular ends of bones and also where it is found directly under the skin, i.e., ears and nose. This membrane contains vessels that provide the cartilage with nutrition.

• Connective tissue is made up of a large amount of intercellular matrix of fibers or both and living cells. Some connective tissue cells contain pigment granules. 
• Pigment connective tissues are found in the dermis of the skin, iris, and choroid coat of the eye. 
• Pigment connective tissue is partly built up of stellate, serrated, or lobular pigment cells of ectodermal origin, melanocytes.

Ligaments are the connective tissue that joins the two bones. A sprain, more commonly known as torn ligament, is damage to one or more ligaments in a joint, often caused by trauma or the joint being taken beyond its functional range of motion. So, the correct answer is option B.

• The Haversian canal occurs in the humerus.
• Haversian canals are a series of tubes around narrow channels formed by lamellae. This is the region of bone, called cortical bone.
• Osteons are arranged in parallel to the long axis of the bone. The Haversian canals surround blood vessels and nerve cells throughout the bone and communicate with osteocytes in lacunae through canaliculi.
• This unique arrangement is conducive to mineral salt deposits and storage, which gives the bone tissue its strength.

A protein present in cartilage and bone is chondrin and ossein respectively.

• Bone is a metabolically active tissue composed of several types of cells. These cells include osteoblasts, which are involved in the creation and mineralization of bone tissue, osteocytes, and osteoclasts, which are involved in the reabsorption of bone tissue.
• Cartilage is composed of specialized cells called chondrocytes that produce a large amount of collagenous extracellular matrix, abundant ground substance, that is rich in proteoglycan and elastin fibers. Cartilage is classified into three types, elastic cartilage, hyaline cartilage and fibrocartilage, which differ in relative amounts of cartilage. 

• The Arneth count or Arneth index describes the nucleus of a type of white blood cell called neutrophil in an attempt to detect disease.
• Neutrophils typically have two or three lobes. The Arneth count determines the percentage of neutrophils with one, two, three, four, and five or more lobes.

Cooke-Arneth count, percent distribution of neutrophils in the circulation based on the number of their lobes are shown:

The lifespan of adult RBCs is 120 days but in contrast to the same, the life span of RBCs (Red Blood cells) in newborns is approximately 60 -100 days and the life span of RBC of premature newborns has a shorter life span i.e., 35-50 days.

Hence option A is the correct answer.

• The normal albumin/ globulin ratio in the blood is 2:1.
• Albumin and globulin are the two major proteins found in the blood. The albumin/globulin ratio is the amount of albumin in the blood compared to the amount of globulin in the blood.
• The ratio is primarily used to evaluate liver function but also is an indicator of many other possible problems. The albumin/globulin ratio normal levels are from 0.8 to 2.0.

• Sex chromatin is a densely staining mass within the nucleus of all undivided cells in normal mammalian females. It represents the heterochromatin of inactivated X chromosomes.
• Sex chromatin is found as a drumstick-shaped mass attached to one of the nuclear lobes in neutrophils in normal females.

• Eosinophilia is a condition in which the eosinophil count in the peripheral blood exceeds.
• Eosinophils usually account for less than 7% of the circulating leukocytes. A marked increase in non-blood tissue eosinophil count noticed upon histopathologic examination is diagnostic for tissue eosinophilia.
• Eosinophils help promote inflammation, which plays a beneficial role in isolating and controlling a disease site. For example, eosinophils play a key role in the symptoms of asthma and allergies, such as hay fever. Other immune system disorders also can contribute to ongoing (chronic) inflammation.
• The most common parasitic infections associated with eosinophilia in refugees are the soil-transmitted helminths (trichuriasis, Ascaris, and hookworm), Strongyloides, and Schistosoma as well as many tissue-invasive parasites (e.g. parasites that migrate through human tissues as a part of their life cycle).

Therefore option D is correct.

Blood group antigens are surface markers on the outside of the red blood cell (RBC) membrane. They are proteins and carbohydrates attached to lipid or protein.

Hemoglobin A (HbA), also known as 'Adult hemoglobin':

• It is the most common human hemoglobin tetramer.
• It comprises about 97% of the total RBC hemoglobin.
• It consists of two alpha chains and two beta chains.

• Fetal hemoglobin or foetal hemoglobin (also hemoglobin F, HbF, or α2γ2) is the main oxygen carrier protein in the human fetus. Hemoglobin F is found in fetal red blood cells and is involved in transporting oxygen from the mother's bloodstream to organs and tissues in the fetus.
• It is able to bind oxygen with greater affinity than the adult form, giving the developing fetus better access to oxygen from the mother's bloodstream. It has 2 alpha and 2 gamma chains.

• The life span of platelets is 8 - 9 days. Platelets, also called thrombocytes, are blood cells, whose function is to stop bleeding. Platelets have no nucleus: they are fragments of cytoplasm, which are derived from the megakaryocytes of the bone marrow, and then enter the circulation.
• The unactivated platelets are biconvex discoid structures. The life span of individual platelets is controlled by the internal apoptotic regulating pathway. Old platelets are destroyed by phagocytosis in the spleen and liver.

Blood consists of: RBCs, white blood cells (WBCs), and platelets (suspended in a fluid portion called plasma).

The hematocrit is a ratio of the volume of red blood cells to the volume of all these components together, called whole blood. The value is expressed as a percentage or fraction.

The maximum concentration of Hb found in RBC is 36%.

► Hemoglobin is the iron-containing oxygen transport metalloprotein in the red blood cells of all vertebrates.

► DLC, differential blood count: It gives a relative percentage of each type of white blood cell and also helps reveal abnormal white blood cell populations.
Example: Blasts, Immature Granulocytes, or Circulating Lymphoma cells in the peripheral blood.

The percentage of neutrophils found in DLC is 65%.

• A platelet count of fewer than 150,000 platelets per microliter is lower than normal. If your blood platelet count falls below normal, you have thrombocytopenia.
• However, the risk for serious bleeding doesn't occur until the count becomes very low - less than 10,000 or 20,000 platelets per microliter.

Since, 40,000/mm³ is lower than 150,000/mm³. Hence, the correct option is Option A

Red blood cells plasma membrane contains the following enzymes: ATPases, anion transport protein, glyceraldehyde 3-phosphate dehydrogenase, protein kinases, adenylate cyclase, acetylcholinesterase.

► Among glycolytic enzymes, glyceraldehyde 3-phosphate dehydrogenase is present in red blood cells plasma membrane.
► Whereas no enzymes of the citric acid cycle also known as TCA cycle (tricarboxylic acid cycle) or Krebs cycle is present in RBCs.

• Colloid osmotic pressure is a form of osmotic pressure, which is exerted by protein, known as albumin in a blood vessel's plasma (blood/liquid) that usually tends to pull water into the circulatory system.
• Albumin constitutes approximately 80% of the total oncotic pressure exerted by blood plasma and interstitial fluid. Maintaining the proper pressure ensures that the body tissues maintain the proper levels of liquid.