4) Connective Tissue and 4 Basic Tissues

Question 1

What are the 4 Basic Tissue Types

Answer 1

1. epithelium
2. connective tissue
3. muscle
4. nervous tissue

Question 2

Name three types of muscle tissue and their characteristics

Answer 2

Skeletal muscle: Voluntary, striated, attached to bones.

Cardiac muscle: Involuntary, striated, found in the heart, has intercalated discs.

Smooth muscle: Involuntary, non-striated, found in hollow organs (e.g., intestines).

Question 4

CT vs. Epi tissue

Answer 4

Vascular (most except cartilage)

Lies below the basement membrane

Question 5

Connective tissue

Answer 5

●CT connects epi to rest of the body (via. The reticular
layer of the basement membrane)

● Provides structural and physical support (cartilage,
bone), store energy (fat), and transport materials
throughout the body

● Provides pathways for nerves and blood vessels

● Unlike epi tissue, CT are never exposed to the
environment (always internal)

Question 6

Connective Tissue

Common Characteristics and Things that aren’t so Common

Answer 6

Common Characteristics
● All derived from mesenchyme
● All composed of cells and extracellular matrix (fibers and ground substance) but in varying
proportions

Things not common
● Vascularity (some CT have good blood source whiles do not)
● Wide variation in amounts of fibers/ground substance/ cells

Question 7

What is mesenchyme (CT is derived from it)

Answer 7

The mesenchyme is a multipotent stem cell that can turn into various types of cells

●Fibroblast: Most common - Synthesizes fibers and ground substance

●Macrophage: Phagocytes

●Mast cell: Immune response to foreign particles

●Adipocyte:Produces fat

●Leukocyte: White blood cell

Question 8

What are the CT cells?

Answer 8

● Fibroblasts

● Chondrocytes (cartilage) and osteocytes bone)

● Macrophage

● Mast cells

● Adipocytes

● Leukocytes

Question 9

What are the CT extracellular matrix?

Answer 9

● Fibers – protein fibers – collagen, reticulin and elastin

● Ground substance consists of an aqueous gel of glycoproteins and proteoglycans that occupies the space between cellular and fibrillar elements of the connective tissue.

● It is characterized by a gel-like viscous
consistency. The characteristics of the
ground substance determine the
permeability of the connective tissue layer to solutes and proteins.

Question 10

What are the CT Fibers?

Answer 10

Collagen, Reticular, Elastin

Question 11

CT Fiber: Collagen

Answer 11

Collagen: most abundant

• Looks like a rope w/ 3 individual protein
  fibers twined around each other
• Extremely strong but little flexibility
• Does not branch

●Type I - most common: found in every
connective tissue

●Type II - Cartilage: found in hyaline and elastic cartilage

●Type III: found in reticular fibers, healing wounds, smooth muscle and fetal skin

●Type IV - basement membrane: Provides structural support and acts as a filtration barrier

●Type V: tendon, and muscle sheaths

Mnemonics to Remember
“1 Bone, 2 Cartilage, 3 Mesh, 4 Floor, 5 Tendons More.”

Question 12

CT Fiber: Reticular

Answer 12

Reticular:
* Forms a net
* Composed of small fibers (type III)
* Shorter than collagen
* Branch-like supporting structure to give shape to
various organs (liver, spleen, uterus, lymph nodes)

Question 13

CT Fiber: Elastin

Answer 13

Elastin:
* Elastic properties to stretch and be compressed

• Importing flexibility in the CT where there are found
• Branch-like
• Form lamellar sheets (thin layer, membrane, or plate of tissue, especially in bone.) around arteries
• Dense elastic in ligaments
• When tissue is not being stretched-normally
  disorganized manner
• When tissue is stretched- fibers take on an organized
  structure

Question 14

Types of CT

Answer 14

Ordinary:
Loose connnective tissue (LOCT)
Dense connnective tissue (Dense CT)

Specialized:
Cartilage
Bone
Blood and blood forming tissues

Question 15

What is Loose connnective tissue (LOCT)?

Answer 15

Loose connective tissue - delicate, flexible, not very resistant to stress, well vascularized. All types of connective tissue cells present.
Majority are fibroblasts and macrophages.
Collagen, elastic, and reticular fibers present

○ Found just about everywhere in the body except brain and spinal cord

Function: fills space, cushion & support, stores fat, feeds epithelium, also binds together tissues, organs and their components

Three main types of LOCT in adults:

1. Areolar CT
   Open, loose framework, highly vascular - most common form
2. Adipose Tissue (fat within adipocytes) and limited extracellular space but lots of adipocytes which form a cushion around organs
3. Reticular CT – fine fibrils around organs

Main cells of LOCT are fibroblasts (secrete the components which make up the fibers and ground substance)

Question 16

What is Areolar LOCT?

Answer 16

● Least specialized but most common

● Distributed randomly and crisscross in all directions

● Open framework distorts w/o damage

● Viscous ground substance absorbs shock- elastic fibers return to original shape

● Holds blood vessels and capillary beds- fills spaces

● Examples: separates skin from deeper structures, contains all 3 CT fibers, as well as fat cells

Question 17

What is Adipose tissue- LOCT?

Answer 17

● Dominated by fat cells (adipocytes)
○ Most LOCT contains clusters of fat cells, but adipose tissue refers to larger masses of fat
cells
○ Adipocytes stores lipid in cytoplasm

● Function: absorbs shock, stores fat, and slows heat loss
○ Fat is lost in routine histological preparation so under the microscope adipocytes appear
like ghost cells (hollow) so only cell membrane and nucleus is visible

• Adipose tissue is richly vascularized
• Develops most anywhere
• Good at storing nutrients
• Made of closely packed adipocytes
• Provides reserve food fuel
• Supports and protects organs

Question 18

What is Reticular tissue - LOCT?

Answer 18

● Complex, 3D network of supportive fine reticular fibers
○ Mesh-like, very supportive for soft tissues (liver, spleen, lymph nodes, bone marrow)

● Resembles areolar CT but the fibers are reticular fibers which is more delicate with fibroblasts
○ Reticular cells lie scattered

● To visualize reticular CT, special stains is required since it is so fine

● branching

Question 19

What is DENSE Connective Tissue?

Answer 19

● Contains relatively fewer cells that loose CT

● Predominantly collagen fibers at the expense of little ground substance, poorly vascularized

● Less flexible and more resistant to stress

● 2 types:
○ Dense regular: Collagen bundles are oriented in parallel arrays (has order)

○ Dense irregular: Collagen bundles have no orientation

Question 20

What is DENSE REGULAR Connective Tissue?

Answer 20

● Closely packed collagen bundles
○ Parallel fibers, aligned w/ direction of force

● Resistance to tension

● Parallel to pull

● Mainly consist of fibers

● Makes up tendons and ligaments
Function: high strength attachment and stabilize proteins
Locations:
○ Tendons
○ Ligaments
○ Muscle coverings
○ fascia

Question 21

What is DENSE IREGULAR Connective Tissue?

Answer 21

● Mesh of collagen fibers and some elastic fibers in a viscous matrix

● Thicker fibers

● Irregularly arranged
Function: resist tension from many directions
Location: found in body where tension is exerted
○ Skin
○ Forms joint capsules
○ Fibrous coverings around some organs

Question 22

Specialized CT

Types: supportive and fluid CT

Answer 22

Supportive:
● Cartilage
● Bone/osseous tissue
● Strong framework, few cells, fibrous matrix

Fluid:
● Blood, plasma, lymph
● Blood is a liquid CT composed of a fluid matrix and blood cells

Question 23

Cartilage vs Bone

Answer 23

● Cartilage and Bone are similar to the soft connective tissue in that they are composed of cells,
fibers and ground substance (matrix).

● They differ from the other connective tissue by the presence of substances in the intercellular
matrix that provide firmness (as in cartilage) and rigidity (as in bone).

Question 24

Cartilage Characteristics and the 3 Types

Answer 24

● Avascular! – all types of cartilage have no capillaries running within it

● Composed of chondroblasts & chondrocytes
○ Cells lie in lacunae
○ Chondrocytes lying in lacunae are often binucleate (having two cellular nuclei)

● Chondrocytes receive nutrients from blood vessels in surrounding CT by diffusion through ground
substance (perichondrium) – DICT

● Very tough w/ some flexibility

● Not as hard as bone but not as soft as DCT

● Stands up to compression and extension

3 TYPES:
● Hyaline
● Fibrocartilage
● Elastic