أسئلة المحاضرة التاسعة هستولوجي (قبل التعديل)

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Questions and Answers

What is the primary protein found in the center of elastic fibers?

Elastin (correct)

Collagen

Reticulin

Fibrillin

Which of the following structures is NOT a site where elastic fibers are typically found?

Ligamentum flavum

Bronchioles

Trachea

Spleen (correct)

Which type of fiber is characterized by its ability to form a branching network?

Fibroelastic fibers

Reticular fibers (correct)

Collagen fibers

Elastic fibers

What color can reticular fibers appear when stained with silver?

Black Signup and view all the answers

Which type of glycosaminoglycan is linked to a core protein to form proteoglycans?

Chondroitin sulphate Signup and view all the answers

Which component of connective tissue acts as adhesive material and is coated by glycoproteins?

Amorphous component Signup and view all the answers

In which type of connective tissue can you find synovial fluid?

Mucoid connective tissue Signup and view all the answers

What does metachromasia refer to when staining tissue?

Appearing as a different color than the dye Signup and view all the answers

Which cell type is primarily responsible for the synthesis of connective tissue matrix and fibers?

Fibroblasts Signup and view all the answers

What is a unique characteristic of pericytes?

They are located around blood capillaries. Signup and view all the answers

In which context are mesenchymal cells most commonly found?

In embryos and during fetal life Signup and view all the answers

What is the primary function of connective tissue?

To support, bind and separate various tissues and organs. Signup and view all the answers

What characterizes the appearance of fibroblasts compared to adipose cells?

Fibroblasts are spindle-shaped and more flat. Signup and view all the answers

Which of the following best describes white collagenous fibers?

Strong, wavy bundles that are resistant to stretch. Signup and view all the answers

What is the primary function of macrophage cells derived from migrating blood monocytes?

Immune response and phagocytosis Signup and view all the answers

How are tropocollagen molecules structured?

They are made of three polypeptide chains twisted around each other to form a triple helix. Signup and view all the answers

Which of the following statements about reticular cells is true?

They provide structural support in lymphatic tissues. Signup and view all the answers

What color do white collagenous fibers appear when viewed microscopically?

White. Signup and view all the answers

What types of tissues can collagenous fibers be found in?

In tendons, ligaments, and skin dermis. Signup and view all the answers

What aspect of fibroblasts contributes to the healing of wounds?

Their role in synthesizing connective tissue components. Signup and view all the answers

Which characteristic sets plasma cells apart from other connective tissue cells?

They produce antibodies. Signup and view all the answers

Which of the following characteristics is true of yellow elastic fibers?

They branch and can form elastic membranes. Signup and view all the answers

Which type of connective tissue is primarily characterized by the presence of reticular fibers?

Lymphoid tissue. Signup and view all the answers

What enzymatic action can digest yellow elastic fibers?

Pancreatic elastase. Signup and view all the answers

What characteristic defines the M1 'killer' macrophages?

They have a phagocytic function. Signup and view all the answers

Which statement most accurately describes the reticular fibers?

They are found mainly in loose connective tissue. Signup and view all the answers

What is a major function of the M2 'repair' macrophages?

They promote wound healing and tissue repair. Signup and view all the answers

What type of cell acts as a multipotent stem cell in the context of connective tissue?

Undifferentiated mesenchymal cells (UMCs) Signup and view all the answers

Which of the following is NOT a characteristic of the macrophages described?

They have a limited role in presenting antigens. Signup and view all the answers

How are the M1 macrophages primarily identified histologically?

By their pale basophilic staining. Signup and view all the answers

What is the main difference in the types of adipocytes derived from lipoblasts?

White adipocytes are fully differentiated cells. Signup and view all the answers

Which staining technique is typically used to visualize reticular fibers?

Silver stain Signup and view all the answers

Which of the following is a life-threatening condition associated with Marfan syndrome?

Aortic aneurysms Signup and view all the answers

What component of connective tissue is typically synthesized by a class of integral membrane proteins?

Glycosaminoglycans Signup and view all the answers

In which type of connective tissue can you typically find reticular fibers that form a network?

Parenchymatous organs Signup and view all the answers

What is the primary role of glycoproteins in connective tissue?

Adhesive material Signup and view all the answers

Which staining technique would result in a reddish-purple color due to the presence of glycosaminoglycans?

Toluidine blue Signup and view all the answers

What role do pericytes play in connective tissue?

They help in the synthesis of connective tissue matrix. Signup and view all the answers

What is the primary cell type responsible for producing elastic fibers in connective tissue?

Smooth muscle cells Signup and view all the answers

Which statement accurately reflects the characteristics of fibroblasts?

They are primarily responsible for the synthesis of the connective tissue matrix. Signup and view all the answers

What characteristic distinguishes metachromasia in histological staining?

Differential color due to dye interaction Signup and view all the answers

Which feature is associated with white collagenous fibers?

They appear blue or red when stained. Signup and view all the answers

What is a key feature of adipose cells compared to fibroblasts?

Adipose cells store energy as fat, while fibroblasts do not. Signup and view all the answers

Which type of glycosaminoglycan is commonly found in cartilage and bone?

Chondroitin sulfate Signup and view all the answers

What is a defining characteristic of yellow elastic fibers?

They can be degraded by pancreatic elastase enzyme. Signup and view all the answers

What is the approximate length of a tropocollagen molecule?

280 nm Signup and view all the answers

What distinguishes plasma cells from other cells within connective tissue?

Plasma cells secrete antibodies as part of the immune response. Signup and view all the answers

Which connective tissue type is NOT directly mentioned as containing collagenous fibers?

Adipose tissue Signup and view all the answers

Which type of cell is most numerous in the loose connective tissue?

Fibroblasts Signup and view all the answers

Which cell type is described as having a central, large, oval, and vesicular nucleus?

Pericytes Signup and view all the answers

What unique property distinguishes white collagenous fibers from yellow elastic fibers?

White collagenous fibers exhibit wavy structure. Signup and view all the answers

Which statement is true regarding the structural arrangement of fibroblasts?

They synthesize tropocollagen molecules. Signup and view all the answers

What type of connective tissue is identified by the presence of branching spindle-shaped cells?

Loose connective tissue Signup and view all the answers

What is the origin of macrophages that reside in connective tissue?

Migrating blood monocytes. Signup and view all the answers

How do the branches of yellow elastic fibers contribute to their function?

They allow for better stretching and recoil. Signup and view all the answers

Which of the following is a primary characteristic of reticular fibers?

They form a network of thin fibrils. Signup and view all the answers

What is a primary characteristic of M1 'killer' macrophages?

They primarily function in phagocytizing foreign bodies. Signup and view all the answers

Which of the following statements about M2 'repair' macrophages is accurate?

They play a role in tissue repair and secrete growth factors. Signup and view all the answers

What is the main feature of reticular cells in loose connective tissue?

They have branching processes that support parenchymal cells. Signup and view all the answers

Which staining technique is often utilized to visualize reticular fibers?

Silver stain. Signup and view all the answers

What type of cells derive from lipoblasts in the context of adipose tissue?

Brown adipocytes. Signup and view all the answers

What cellular feature distinguishes M1 macrophages from M2 macrophages?

M1 macrophages are involved in phagocytosis and antigen presentation. Signup and view all the answers

What type of organelles are typically abundant in macrophages, especially the M1 type?

Lysosomes and phagosomes. Signup and view all the answers

Which type of connective tissue is primarily characterized by the presence of a reticular stroma?

Loose connective tissue. Signup and view all the answers

Study Notes

Connective Tissue (CT)

CT supports, binds, and separates various tissues and organs
Two types:
- Connective tissue proper
- Special types: cartilage, bone, blood, hematopoietic tissue, lymphoid tissue

Connective Tissue Proper

Fibers:
- White collagenous fibers: white, strong, resist stretch, form wavy bundles (branching bundles, single fibers don't branch), affected by boiling (converted to gelatin), destroyed by acids/alkalis, digested by pepsin and collagenase enzymes
- Yellow elastic fibers: yellow, thin, long, highly refractile (able to reflect light), elastic, recoil after stretch, branch, found in aorta walls, digested by pancreatic elastase
- Reticular fibers: very thin, form network, argyrophilic (affinity for silver), found in stroma of parenchymatous organs, reticular lamina of basement membranes
Matrix (Ground Substance):
- Macromolecules: multi-adhesive glycoproteins
- Hyaluronic acid, soft, jelly-like, not linked to protein core, synthesized by hyaluronan synthases
- Chondroitin sulfate: linked to protein core, forming proteoglycans; found in cartilage and bone; heparan sulfate in basal lamina
- Glycoproteins: examples: chondronectin (cartilage), osteonectin (bone), fibronectin (CT proper). Act like adhesives
Cells:
- Fibroblasts: responsible for synthesizing CT matrix and fibers; spindle-shaped, branched, central nucleus
- Macrophages: phagocytize foreign bodies like bacteria; important in wound healing; large, rounded cell with pseudopodia (processes); nucleus is eccentric, small, oval and pale
- Mast cells: found in connective tissue, involved in inflammatory response.
- Plasma cells: produce antibodies; small, round nuclei
- Lymphocytes (important parts of the immune system): important in responding to infectious pathogens.
- Adipose: fat cells; store energy; spherical shaped
- Leukocytes: white blood cells
- Other cells: mesenchymal cells, pericytes, reticular cells

Connective Tissue Fibers - Characterization

White collagenous fibers: color: white; resistant to stretch; wave-like bundles; branching bundles are found; single fiber does not branch; affect by boiling, converted in gelatin; destroyed by acids and alkalis; digested by pepsin and collagenase
Yellow elastic fibers: color: yellow; thin, long, highly refractive meaning able to reflect light; elastic in nature; recoils after release of stretch; branch and may form elastic membranes e.g. in the aorta walls; not affected by boiling; digested by pancreatic elastase enzyme

Types and Sites of Collagen

Type I: Bone, tendon, teeth, dermis
Type II: Hyaline and elastic cartilage
Type III: Reticular stroma of liver, spleen, kidney, lymph nodes
Type IV: Basal lamina of basement membranes
Type V: Basal lamina of the placenta

Staining

H&E: Acidophilic
Mallory Trichrome Stain: Collagen fibers (blue)
Van Gieson's Stain: Collagen fibers (red)
Verhoeff's Stain: Elastic fibers (black)
Silver stain: reticular fibers (black)
PAS: magenta colored (polysaccharides)

Fixed vs. Free CT Cells

Fixed: Undifferentiated mesenchymal, fibroblasts, adipose, reticular, macrophages (originate locally, remain in the CT).
Free: Mast cells, free macrophages, plasma, pigment cells, blood leukocytes (originate elsewhere, temporarily in CT)

Undifferentiated Mesenchymal Cells (UMCs)

Mesodermal cells of the embryo
Can divide
Differentiate into various CT cells (fibroblasts, chondrocytes, etc).
Found in embryonic connective tissue (mesenchymal and mucoid CT), pulp of deciduous teeth

Fibroblasts

The most common CT cells; responsible for synthesizing CT matrix and fibers
Responsible for growth, repair, and healing of wounds
Commonly found in loose CT; spindle shaped, contain central nuclei, pale basophilic cytoplasm containing free ribosomes

Macrophages

Originate from blood monocytes (originally developing from UMCs in the bone marrow)
Cannot divide, fully differentiated
Primarily in loose CT
Large, rounded with pseudopodia (processes)
Second most common cell in loose CT
Eccentric, small, kidney-shaped/irregular, single, and pale

Reticular cells

UMC (undifferentiated mesenchymal cell).
Cannot divide, fully differentiated.
Reticular stroma of parenchymal organs.

Adipocytes

Brown Adipocytes:
- Multi-nucleated
- Many fat droplets
- In sites of brown adipose CT
- 10 times smaller than white adipocytes
- Oval shaped cells, with single central nucleus
- Cytoplasm is acidophilic (with many vacuoles due to dissolved fat droplets)
White Adipocytes:
- Multi-nucleated
- One fat globule
- In sites of white adipose CT
- Also in loose CT
- 10 times larger than brown adipocytes
- Oval shaped cells, with peripheral nucleus (signet ring appearance)
- Cytoplasm contains a large fat globule

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