Histology of Connective Tissue

Question 1

Connective tissue is derived from _ germ cell layer

Answer 1

Connective tissue is derived from mesoderm germ cell layer
* Mesoderm also gives rise to muscle tissue

Question 2

Two categories of connective tissue include _ and _

Answer 2

Two categories of connective tissue include connective tissue proper and specialized connective tissue
* Connective tissue proper is protecting and supporting organs/tissues/structures
* Specialized connective tissue has additional roles

Question 3

Four types of connective tissue proper

Answer 3

Connective tissue proper provides resistance to pulling, stretching

Four types:
1. Dense regular connective tissue
2. Dense irregular connective tissue
3. Loose (areolar) connective tissue
4. Reticular connective tissue

Question 4

Four main types of specialized connective tissue:

Answer 4

Four main types of specialized connective tissue:
1. Blood transports nutrients and oxygen
2. Cartilage provides template for bone growth
3. Bone home for hematopoietic precursor cells
4. Adipose tissue stores energy in form of lipids

Question 5

How does the composition of connective tissue differ from epithelial, muscle, and nerve tissue?

Answer 5

Connective tissue (especially connective tissue proper) has abundant extracellular matrix
* The ECM carries out its main functions
* ECM is composed of fibers and amorphous ground substance

Question 6

Fibers in the ECM are made of _ and they are really good at resisting _ forces

Answer 6

Fibers in the ECM are made of proteins and they are really good at resisting tensile forces
* Fibers run parallel in tendons to resist forces in the direction that the muscle produces force

Question 7

Two types of fibers are _ and _

Answer 7

Two types of fibers are elastic and collagen

Question 8

Elastic fibers are thin, structural proteins that allow for incredible elasticity due to a protein called _

Answer 8

Elastic fibers are thin, structural proteins that allow for incredible elasticity due to a protein called elastin
* Elastin forms the inner core of elastic fibers
* It is composed of short peptide chain that are cross-linked in a way that allows for extension and retraction

Question 9

The cross-links of elastin are composed of two amino acids, _ and _

Answer 9

The cross-links of elastin are composed of two amino acids, desmosine and isodesmosine which are only found in elastin

Question 10

Elastic fibers are found in tissues that need to stretch, expand, and return their shape such as _

Answer 10

Elastic fibers are found in tissues that need to stretch, expand, and return their shape such as walls of arteries, bronchi, bronchioloes, ligaments

Question 11

The most common type of fiber found in the ECM is _

Answer 11

The most common type of fiber found in the ECM is collagen

Question 12

Type _ collagen is found in bone, skin, tendons, dentin, ligaments, fascia, scar tissue, fibrocartilage, organ capsules, cornea

Answer 12

Type I collagen is found in bone, skin, tendons, dentin, ligaments, fascia, scar tissue, fibrocartilage, organ capsules, cornea

Question 13

Type _ collagen is the most common among the collagen subtypes and makes up about 90% of the collagen in our body

Answer 13

Type I collagen is the most common among the collagen subtypes and makes up about 90% of the collagen in our body

Question 14

The key function of type I collagen is to _

Answer 14

The key function of type I collagen is to resist tension

Question 15

The stripy appearance to collagen is due to a complex, staggered arrangement of small molecules called _

Answer 15

The stripy appearance to collagen is due to a complex, staggered arrangement of small molecules called tropocollagen

Question 16

Type _ collagen is found in the hyaline cartilage matrix

Answer 16

Type II collagen is found in the hyaline cartilage matrix

Question 17

The nucleus pulposus of vertebral discs and the vitreous body of the eye is type _ collagen

Answer 17

The nucleus pulposus of vertebral discs and the vitreous body of the eye is type II collagen

Question 18

The primary function of type II collagen is to _

Answer 18

The primary function of type II collagen is to resist pressure
* These fibers are thin

Question 19

Hyaline cartilage appears smooth and glassy due to a blend between type II collagen and _

Answer 19

Hyaline cartilage appears smooth and glassy due to a blend between type II collagen and glycosaminoglycans

Question 20

Type III collagen fibers are extremely fine and delicate; they provide structural support to _

Answer 20

Type III collagen fibers are extremely fine and delicate; they provide structural support inside hematopoietic organs like bone marrow, spleen, lymph nodes

Question 21

Collagen III fibers are also called _

Answer 21

Type III collagen fibers are also called reticulin or reticular fibers
* Latin for network
* * Can be seen seen with silver stain

Question 22

Vascular Ehlers-Danlos syndrome is a genetic disorder of connective tissues; specifically, EDS is a defect in _

Answer 22

Vascular Ehlers-Danlos syndrome is a genetic disorder of connective tissues; specifically, EDS is a defect in transcribing DNA/ translating mRNA that encodes type III collagen

Question 23

What are the signs/symptoms of Ehlers-Danlos Syndrome?

Answer 23

EDS causes thin, easily buised, fragile skin that can sometimes be excessively stretchy
* Also causes hyperflexible joints
* Sometimes causes emergent rupture of bowel or large arteries since type III usually surrounds smooth muscle cells

Question 24

Type IV collagen’s main function is to form _

Answer 24

Type IV collagen’s main function is to form meshwork of fibers in the basal lamina of basement membranes
* Functions to support and anchor epithelial cells
* Also aids filtration
* Scaffold for cell migration

Question 25

_ is a watery, gelatinous, clear material that fills the space between fibers of the ECM and connective tissue cells

Answer 25

**Ground substance** is a watery, gelatinous, clear material that fills the space between fibers of the ECM and connective tissue cells * Structured such that small molecules and metabolites can diffuse through it * It acts as a barrier to invaders * Also good lubricant

Question 26

Ground substances also contain large molecules called glycosaminoglycans (GAGs), most of which are bound to _ to form _

Answer 26

**Ground substances** also contain large molecules called glycosaminoglycans (GAGs), most of which are bound to **proteins** to form **proteoglycans** * Proteoglycans act as *stabilizer* and *barrier* for connective tissue

Question 27

Ground substance also contains glycoproteins like _ which is a key protein in the basal lamina and fibronectin

Answer 27

Ground substance also contains glycoproteins like **laminin** which is a key protein in the *basal lamina* and *fibronectin*

Question 28

What is fibronectin?

Answer 28

**Fibronectin** is an ECM component involved in wound repair, embryogenesis, and cell-to-cell adhesion

Question 29

Macrophages, lymphoid cells, plasma cells, and granulocytes are all types of (transient/ resident) cells of the connective tissue

Answer 29

Macrophages, lymphoid cells, plasma cells, and granulocytes are all types of **transient cells** of the connective tissue

Question 30

Pericytes, adipocytes, mast cells, and fibroblasts are all examples of (transient/ resident) cells of connective tissue

Answer 30

Pericytes, adipocytes, mast cells, and fibroblasts are all examples of **resident cells** cells of connective tissue

Question 31

Pericytes

Answer 31

**Pericytes** are pluripotent cells that are similar to fibroblasts and play a role in modifying capillary blood flow

Question 32

Fibroblasts

Answer 32

**Fibroblasts** are the "master chef"; they have the ability to make collagen, elastic fibers, other parts of the ground substance

Question 33

How do we know if fibroblasts are active or inactive based on appearance?

Answer 33

**Inactive fibroblasts** have an *oval* nucleus with many nucleoli **Active fibroblasts** have a *fusiform* shape and many golgi complexes and an extensive RER

Question 34

(True/False) Fibroblasts normally undergo mitosis

Answer 34

False; Fibroblasts **do not** normally undergo mitosis * Except when wound healing

Question 35

We find dense regular connective tissue proper mainly in _ and _

Answer 35

We find **dense regular** connective tissue proper mainly in **ligaments** and **tendons** * Parallel orientation makes dense regular good at withstanding tension in one direction

Question 36

What are the key histologic features of **dense regular**?

Answer 36

**Dense regular**: * Densely packed * Parallel bundles of Type I * Few fibroblasts and scant ground substance

Question 37

What are the key histologic features of **dense irregular**?

Answer 37

**Dense irregular**: * Densely packed * Randomly oriented bundles of type I * Few fibroblasts and scant ground substance * Collagen bundles are in random/irregular directions

Question 38

Where do we mostly find dense irregular connective tissue proper?

Answer 38

**Dense irregular** is normally found in **organ capsules** and the **deep dermis of the skin** * Places that are susceptible to multidirectional pulling forces

Question 39

What are the key histologic features of **loose (areolar)** connective tissue?

Answer 39

**Loose (areolar) connective tissue**: * Numerous fibroblasts and fine collagen fibers interspersed with areas of clear ground substance * Contains numerous cell types (fibroblasts, plasma cells, macrophages)

Question 40

Where do we find loose (areolar) connective tissue?

Answer 40

**Loose (areolar) tissue** is mostly in the **lamina propria** of the GI tract, around **vessels and nerves**, **upper dermis**

Question 41

What are the key histologic features of reticular connective tissue?

Answer 41

**Reticular connective tissue**: * Type III collagen fibers in net-like arrangement

Question 42

Where do we find reticular connective tissue?

Answer 42

**Reticular connective tissue** is found in the **bone marrow, lymph nodes, and spleen** * Delicate, supportive framework

Question 43

The most prevalent form of connective tissue in the body is _

Answer 43

The most prevalent form of connective tissue in the body is **loose (areolar)** connective tissue * It serves as a packing material that fills in otherwise unoccupied spaces in the body

Question 44

Reticular connective tissue is composed of type _ collagen

Answer 44

Reticular connective tissue is composed of **type III collagen (reticulin)** fibers, arranged in an interwoven, net-like pattern