Connective Tissue Overview

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Questions and Answers

What is the primary role of osteoclasts in bone physiology?

  • Formation of cartilage models
  • Production of osteoid matrix
  • Activation of osteoblasts
  • Bone degradation and reabsorption (correct)

During indirect ossification, what is the first event that occurs?

  • Growth of the epiphyseal plates
  • Formation of the hyaline cartilage (correct)
  • Division of chondroblasts
  • Replacement of cartilage with bone tissue

How does calcitonin affect osteoclast activity?

  • It inhibits osteoclasts (correct)
  • It stimulates osteoblast secretion
  • It activates osteoclasts
  • It has no effect

Which process describes the fusion of ossification centers to form spongy bone?

<p>Intramembranous ossification (C)</p> Signup and view all the answers

What structural change occurs in long bones as they grow in length?

<p>The epiphysis is pushed away from the diaphysis (B)</p> Signup and view all the answers

What primarily constitutes the structural integrity of an osteon?

<p>Collagen fibers in parallel orientation (D)</p> Signup and view all the answers

Which of the following correctly describes the fate of osteoblasts after matrix formation?

<p>They can transform into quiescent bone-lining cells or die by apoptosis (C)</p> Signup and view all the answers

What is the significance of osteocytes in bone physiology?

<p>They respond to mechanical forces affecting matrix stiffness (C)</p> Signup and view all the answers

What characterizes the composition of spongy bone compared to compact bone?

<p>Irregular lamellae forming a 3D trabecular network (C)</p> Signup and view all the answers

What is the role of osteoprogenitor cells in bone tissue?

<p>They serve as a pool of undifferentiated cells capable of becoming osteoblasts (B)</p> Signup and view all the answers

Which statement correctly describes the composition of red blood cells?

<p>Red blood cells contain approximately 66% water and 33% proteins. (A)</p> Signup and view all the answers

What is the role of the Rhesus (Rh) antigen in blood classification?

<p>It indicates the presence or absence in blood type determination. (C)</p> Signup and view all the answers

Which of the following accurately describes the differences between granular and agranular white blood cells?

<p>Granular leukocytes can be identified by cytoplasmic granules; agranular do not have them. (B)</p> Signup and view all the answers

What is the significant consequence of homozygosity in sickle-cell anemia?

<p>Homozygosity leads to severe health complications and can be deadly. (A)</p> Signup and view all the answers

How do white blood cells migrate to sites of infection?

<p>They adhere to endothelial cells and then squeeze through them. (C)</p> Signup and view all the answers

Which glycosaminoglycan (GAG) is unique for not containing any sulphate?

<p>Hyaluronic Acid (B)</p> Signup and view all the answers

What is the primary role of fibronectin in connective tissue?

<p>Cell adhesion and migration (D)</p> Signup and view all the answers

Which function is NOT associated with connective tissue proper?

<p>Hormonal regulation of metabolism (D)</p> Signup and view all the answers

Matrix Metalloproteinases are activated by which of the following elements?

<p>Zinc (D)</p> Signup and view all the answers

Which type of connective tissue is characterized as loose and amorphous, found in specific anatomical locations like the umbilical cord?

<p>Mucous connective tissue (B)</p> Signup and view all the answers

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Flashcards

GAGs (Glycosaminoglycans)

A group of complex carbohydrate molecules that play crucial roles in the structure and function of connective tissues. They are often negatively charged and attract water, contributing to the viscosity and elasticity of the ECM.

Fibronectin

A major component of the ECM, it acts as a 'bridge' between cells and various components of the ECM, including collagen. It is essential for cell adhesion, migration, and tissue repair.

Mucous connective tissue (Wharton's jelly)

A type of connective tissue found in various locations, including the umbilical cord, aqueous humor of the eye, and dental pulp. It is characterized by its loose and amorphous structure, with a high water content.

Loose connective tissue (areolar)

A type of connective tissue that is less dense than dense connective tissue. It is rich in cells, blood vessels, and ECM, and it plays a vital role in nutrient exchange and waste removal. Found throughout the body, it provides support and flexibility.

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Matrix metalloproteinases (MMPs)

A group of enzymes crucial for ECM remodeling. They break down ECM components in physiological processes like tissue development and wound healing, and pathological conditions like inflammation or tumor invasion.

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Osteon

A structural unit of compact bone, consisting of concentric rings of lamellae surrounding a central Haversian canal containing blood vessels and nerves.

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Lamellae

Thin layers of compact bone tissue that are arranged in concentric circles around the Haversian canal.

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Osteocytes

Mature bone cells trapped within the lacunae of bone tissue, responsible for maintaining bone health and responding to mechanical stress.

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Osteoblasts

Cells that are responsible for forming new bone tissue by secreting bone matrix and collagen fibers. They have receptor for parathyroid hormone which regulates calcium metabolism.

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Osteoprogenitor Cells

Undifferentiated stem cells present in the periosteum and endosteum that can differentiate into osteoblasts and replace themselves. They can form a single layer.

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Intramembranous ossification

A type of bone formation where pre-osteoblasts in the mesenchyme differentiate into osteoblasts which create osteoid, the non-mineralised matrix of bone. The bone matrix develops into trabeculae, and some osteoblasts become trapped within the matrix and become osteocytes. These ossification centers fuse to create spongy bone. The spaces between trabeculae later become filled with red bone marrow.

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Endochondral ossification

A type of bone formation where cartilage is replaced by bone tissue. This process involves two key steps: the formation of hyaline cartilage, and the growth and subsequent replacement of the cartilage with bone tissue.

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Epiphyseal plate

The region at the end of a long bone where growth occurs. It is composed of cartilage cells arranged in tall stacks, where the upper cells divide quickly. These cells are responsible for pushing the epiphysis away from the diaphysis, leading to the lengthening of the bone.

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What is sickle-cell anemia?

A type of anemia caused by a mutation in the beta chain of the hemoglobin molecule. This mutation results in the substitution of the 287th amino acid.

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What is emigration (diapedesis)?

The process by which white blood cells exit the bloodstream and enter tissues to fight infections. This involves leukocytes adhering to and squeezing through the endothelial cells lining blood vessels.

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What are granulocytes?

White blood cells that contain granules in their cytoplasm. These granules are stained differently and help classify different types of granulocytes.

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What are agranulocytes?

A type of white blood cell that does not contain visible granules in its cytoplasm. Examples include lymphocytes and monocytes.

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What is hemoglobin?

The protein found in red blood cells that is responsible for carrying oxygen to the body's tissues and carbon dioxide back to the lungs. It consists of four globin chains and a heme group containing iron.

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Study Notes

Connective Tissue

  • Connective tissue is composed of various cells derived from mesodermal origin
  • Three types: connective tissue proper (mucous, loose, dense, adipose), supportive connective tissue (cartilage, bone), and liquid connective tissue (blood, lymphoid)
  • Components include cells, fibers, and an extracellular matrix (ECM)
  • ECM is made of fibrillary components (collagen, reticular, elastic fibers) and ground substance (water, electrolytes, glycoproteins, glycosaminoglycans, proteoglycans, enzymes)

Connective Tissue Cells

  • Fibroblasts are the main cells, responsible for synthesizing collagen, elastic, and reticular fibers, and ECM carbohydrates
  • Macrophages (histiocytes) originate from bone marrow or circulating monocytes. They have a defense function, phagocytosing microbes, damaged cells, and debris. They present antigens and secrete cytokines, enzymes, and are involved in tissue healing and development.

Fibroblast Types

  • Type I: Common in skin, bone, tendon, cornea
  • Type II: Cartilage
  • Type III: Reticular fibers, loose connective tissue, blood vessel walls, dermis
  • Type IV: Basal lamina of epithelium, kidney glomeruli

Other Connective Tissue Cells

  • Mast cells: Derived from bone marrow, mediate inflammation, hypersensitivity, and allergies.
  • Leukocytes: (neutrophils, lymphocytes, monocytes, eosinophils, basophils) enter connective tissue from blood
  • Plasma cells: Produce antibodies by B lymphocytes, have a short lifespan (2-4 weeks)
  • Adipocytes: Nucleus and thin cytoplasm are displaced peripherally, due to fat accumulation.

Fibrous Components

  • Collagen: Most abundant, high tensile strength, resisting mechanical stress
  • Reticular fibers: Branched, provide a supporting network, found in various organs
  • Elastic fibers: Branched, allow tissues to respond to stretch and distension

Extracellular Matrix (ECM)

  • ECM provides scaffolding, support, and binding for tissues and organs
  • Involved in transport of metabolites
  • Involved in tissue repair

Ground Substance

  • Contains proteoglycans (core proteins+glycosaminoglycans (GAGs))
  • GAGs are hydrated molecules, viscous and shock-absorbent
  • Hyaluronic acid, dermatan sulfate, chondroitin sulfate, heparin, heparin sulfate, keratan sulfate
  • Fibronectin and laminin: Multiadhesive glycoproteins

Matrix Metalloproteinases (MMPs)

  • Involved in the degradation of ECM components in physiological (morphogenesis, wound healing), pathological (inflammation, atherosclerosis, tumor invasion, fibrogenesis) conditions.

Connective Tissue Propper Types

  • Mucous: (Warthon's jelly): Loose, amorphous, found in umbilical cord, aqueous humor, dental pulp
  • Loose: (Areolar): Less fibers, viscous, gel-like, contains capillary beds, site for immune and inflammatory reactions, found in lamina propria, submucosa of hollow organs, and tunica intima of blood vessels.
  • Dense regular: Fibers run in parallel (tendons, ligaments), or orthogonal (cornea). High resistance to stress
  • Dense irregular: Randomly arranged fibers, surrounding organs

Adipose Tissue

  • Unilocular (white): Energy storage, insulation, in adults
  • Multilocular (brown): Heat production, in children and hibernating animals

Cartilage

  • Composed of cells (chondroblasts/chondrocytes) and ECM
  • Types: hyaline, elastic, fibrocartilage
  • Functions: Supporting skeletal structures, framework for respiratory system, smooth surface for joint movement

Bone Tissue

  • Supports the body, protects organs, provides leverage for muscle action, stores calcium and phosphorus
  • The ECM is strongly mineralized
  • Types: long bones, flat bones, short bones
  • Composed of osteocytes, and ECM containing calcium phosphate crystals and collagen fibers

Blood

  • Delivers oxygen, removes wastes, regulates temperature, pH, and fluid volume.
  • Transports nutrients, hormones, and antibodies
  • Contains plasma (55%): Mostly water, proteins (albumin, globulins, fibrinogen), electrolytes, nutrients, gases, regulatory substances, waste products
  • Contains formed elements (45%): Erythrocytes (red blood cells), leukocytes (white blood cells), and platelets.

Lymphatic System

  • One-way vessel system (tissues to heart)
  • Lymph transports fluid from tissues back to blood
  • Lymph nodes filter lymph, communicate and process information
  • Cells within lymph nodes include: macrophages, lymphocytes, dendritic cells
  • Includes: spleen, thymus, lymph vessels, lymph nodes, macrophages, lymphocytes, dendritic cells.

Blood Cells

  • Erythrocytes: Transport oxygen, lack a nucleus
  • Leukocytes: Fight infection, various types: neutrophils, lymphocytes, monocytes, eosinophils, basophils
  • Thrombocytes (Platelets): Involved in blood clotting

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