Lesson 7

Question 1

-stellate or spindle-shaped cells with large vesicular nucleus rich in euchromatin
-with scanty, acidophilic cytoplasm

(Scanty means sparse or small in amount)

Answer 1

Mesenchymal Cells

Question 2

Large, vesicular, and rich in euchromatin.

Answer 2

Mesenchymal Cells

Question 3

Where are mesenchymal cells most prominent?

Answer 3

Perivascular area.

Perivascular spaces (PVSs) are fluid-filled spaces around small blood vessels in the brain. They are also known as Virchow-Robin spaces.

Question 4

What is the primary means through which metaplasia occurs in connective tissue?

Answer 4

Mesenchymal cells.

Metaplasia, a process where one type of cell changes into another type

mesenchymal cells, which are undifferentiated stem cells in connective tissue, can transform into other types of connective tissue cells under specific conditions.

Question 5

They are precursors of most connective tissue cells.

Answer 5

mesenchymal cells

Question 6

How do reticular cells compare in size to fibrocytes?

Answer 6

Reticular cells are larger than fibrocytes.

Question 7

What connective tissue type are reticular cells associated with?

Answer 7

Reticular connective tissue.

Question 8

Where can a network of reticular fibers be found?

Answer 8

Lymphoid organs.

Question 9

What is the appearance of the reticular cell nucleus in H&E staining?

Answer 9

Large and lightly stained.

Question 10

What are the functions of reticular cells?

Answer 10

1. Producer of reticular fibers.
2. Stem cell for bone marrow elements and macrophages.
3. May have phagocytic action.

Question 11

What is the most common fixed cell in loose connective tissue?

Answer 11

Fibroblasts.

Question 12

What substances do fibroblasts produce?

Answer 12

Fibrous and amorphous intercellular substances.

Question 13

How does the shape of fibroblasts vary depending on their location?

Answer 13

1. Elongated and fusiform when associated with fibers.
2. Rounded when not directly associated with fibers.

Question 14

What is the general shape of the fibroblast nucleus?

Answer 14

Ovoid, although fusiform or elongated shapes may occur.

Question 15

How does the cytoplasm of young fibroblasts appear in H&E staining?

Answer 15

Abundant and basophilic.

Question 16

What are the potential functions of protein synthesized by young fibroblasts?

Answer 16

1. Growth (formation of more fibroblasts).
2. Secretion (production of protein intercellular substances).

Question 17

How do fibrocytes differ from young fibroblasts in appearance?

Answer 17

1. Cytoplasm is difficult to see.
2. Nucleus is pale, thinner, and smaller with less chromatin.

Question 18

What organelles are abundant in active fibroblasts and indicate protein synthesis?

Answer 18

RER and a well-developed Golgi apparatus.

Question 19

What molecules do fibroblasts produce to form fibers?

Answer 19

Tropocollagen molecules

Question 20

Where does the polymerization of tropocollagen into microfibrils occur?

Answer 20

Outside the fibroblasts.

Question 21

What is the combination of young fibroblasts and capillary buds called , that repair sizable connective tissue defects?

Answer 21

Granulation tissue.

Question 22

What is the initial color of granulation tissue, and why?

Answer 22

Pink-to-red because of numerous capillaries.

Question 23

Why does granulation tissue become paler over time?

Answer 23

Fibroblasts produce more collagenic fibers, squeezing the capillaries and reducing blood flow.

Question 24

What does granulation tissue eventually become?

Answer 24

A collagenic scar

Question 25

These are **large cells filled with granules which are metachromatic** when **stained** with **certain basic aniline dyes**; the metachromasia is due to the presence of strongly acidic sulfated mucopolysaccharides;

Answer 25

Mast Cells (Tissue Basophils)

Question 26

What **causes the metachromatic property** of mast cell granules?

Answer 26

**Strongly acidic** **sulfated mucopolysaccharides.**

Question 27

Mast Cells: What are the differences in the size and shape of mast cells among species?

Answer 27

1. **Mouse and rat:** Large, round or ovoid. 1. **Humans:** Larger than in mice and rats, similar shape. 1. **Guinea pigs**: Contain intensely stained granules that obscure cell shape.

Question 28

What substances are contained in mast cell granules?

Answer 28

1. Heparin, 1. histamine, 1. serotonin. ## Footnote The substances contained in mast cell granules include **heparin**, **histamine**, and in some species like the **rat and mouse**, **serotonin** is also present.

Question 29

What are the **functions of histamine** in mast cells?

Answer 29

1. **Causes contraction of smooth muscle cells** and, 1. **increases the permeability** of capillaries and venules.

Question 30

What additional substances **are found in mast cell granules?**

Answer 30

1. Eosinophil chemotactic factor, 1. neutrophil chemotactic factor, 1. neutral proteases (e.g., tryptase, chymase), 1. enzymes like peroxidase and 1. β-glucuronidase.

Question 31

What are some substances **synthesized** by mast cells?

Answer 31

1. Leukotrienes, 1. prostaglandins, 1. and cytokines (e.g., platelet-activating factor, bradykinins, interleukins).

Question 32

What is the primary specialization of macrophages?

Answer 32

Phagocytosis.

Question 33

What are macrophages also called?

Answer 33

Histiocytes or clasmatocytes.

Question 34

What type of nucleus do macrophages have?

Answer 34

Oval and indented on one side, kidney- or bean-shaped.

Question 35

How does the nucleus of a macrophage differ from that of fibroblasts?

Answer 35

is slightly smaller, darker, and indented on one side.

Question 36

From what do macrophages develop?

Answer 36

1. Pre-existing mesenchymal cells, 1. macrophages in loose connective tissue, 1. and monocytes.

Question 37

What are some **substances synthesized** by macrophages?

Answer 37

1. Lysozyme, 1. interferon, 1. prostaglandin, 1. hydrogen peroxide, 1. hydroxy radicals, and 1. superoxide anion.

Question 38

What is the appearance of the macrophage cell membrane?

Answer 38

**Uneven contour with pseudopodia** projecting outward and inward depressions and clefts.

Question 39

What **structures are commonly found** in the **cytoplasm** of macrophages?

Answer 39

**Granules, vacuoles, numerous lysosomes, and residual bodies.**

Question 40

Where are mitochondria typically located in macrophages?

Answer 40

**Congregated** (Flock together) **around the centrosome.**

Question 41

What type of cell **surrounds the endothelial cells of capillaries** or small vessels?

Answer 41

Answer: Pericytes (Cell of Rouget).

Question 42

What type of cells are pericytes classified as?

Answer 42

Undifferentiated mesenchymal cells.

Question 43

What characteristics do pericytes possess?

Answer 43

1. **Characteristics of smooth muscle cells** (contractile) and, **endothelial cells.**

Question 44

What is the function of pericytes under certain conditions?

Answer 44

They **may differentiate** into other cells.

Question 45

What are fat cells called when organized into lobules?

Answer 45

Adipose tissue.

Question 46

How do **fat cells appear in cross-section**?

Answer 46

**Like a signet ring** with the nucleus bulging slightly from one side

Question 47

Why do fat cells appear empty in paraffin sections?

Answer 47

Because fat is dissolved during preparation.

Question 48

What supports individual fat cells within lobules?

Answer 48

Reticular fibers.

Question 49

Why are **abundant capillaries** important in fat cells?

Answer 49

Because of the **constant metabolic activity** in fat cells.

Question 50

From what substances is fat formed?

Answer 50

Glucose and amino acids.

Question 51

What are **foreign body giant cells** formed from?

Answer 51

Fusion of monocytes or macrophages.

Question 52

To enclose or wall off foreign objects or debris too large or resistant for a single phagocyte to destroy. These are-

Answer 52

Foreign Body Giant Cells

Question 53

In which condition are foreign body giant cells common?

Answer 53

Lesions of tuberculosis.

Question 54

What is the principal function of plasma cells?

Answer 54

Production of antibodies (immune globulins).

Question 55

Where do plasma cells differentiate?

Answer 55

In **connective tissue from lymphocytes,** as well as in the **lymph nodes** and **spleen**.

Question 56

In **which type of connective tissue are plasma cells** relatively **uncommon**?

Answer 56

Typical loose connective tissue.

Question 57

Where are plasma cells plentiful?

Answer 57

**In highly cellular connective tissue** supporting *wet epithelial membranes* **lining the respiratory and intestinal tracts.**

Question 58

What are **Russell bodies** in plasma cells?

Answer 58

Spherical inclusions in dilated portions of the ER representing large accumulations of immunoglobulins.

Question 59

**Spherical inclusions** in dilated portions of the ER **representing large accumulations of *immunoglobulins.***

Answer 59

Russell bodies

Question 60

What is any cell containing pigments called?

Answer 60

Pigment cells (e.g., melanocytes).

Question 61

To protect the body from excessive exposure to UV radiation. What cell is responsiblefor it?

Answer 61

melanocytes

Question 62

What system consists of cells capable of phagocytosis and is also called the reticuloendothelial system?

Answer 62

Mononuclear macrophage system.

Question 63

What are some examples of cells in the mononuclear macrophage system?

Answer 63

1. Monocytes of the blood. 1. Fixed and free macrophages of connective tissue. 1. Alveolar phagocytes of the lung. 1. Microglia of the brain. 1. Reticular cells of bone marrow and lymphoid organs. 1. Von Kupffer cells of the liver.

Question 64

What are the main functions of the mononuclear macrophage system?

Answer 64

Answer: **Protect the body from foreign materials** and microorganisms. **Rid** the body of **dead cells**. **Participate in cell-mediated immunity** and humoral antibody response.