connective tissue Flashcards
(13 cards)
Connective tissue,
Connective tissue, as its name suggests, connects body parts. It is found everywhere in the body. It is the most abundant and widely distributed of the tissue types. Connective tissues perform many functions, but they are primarily involved in protecting, supporting, cushioning, and insulating other body tissues.
blood supply in connective tissue
Vascularized means it has a good blood supply.
Most connective tissues (like bone and fat) have lots of blood vessels, which means they:
Get nutrients and oxygen quickly
Heal faster when damaged
🔴 But some connective tissues, like:
Tendons (connect muscle to bone)
Ligaments (connect bone to bone)
…are poorly vascularized, meaning:
They have very few blood vessels
They get less oxygen and nutrients
So they heal very slowly
⚠️ That’s why:
People often say, “I’d rather break a bone than tear a ligament or tendon.”
A broken bone usually heals faster and stronger, because bone has a rich blood supply.
A torn ligament (like an ACL) or tendon can take months to heal — and may need surgery, physical therapy, or might never fully return to normal.
Extracellular matrix
Connective tissues are made up of many different types of cells plus varying amounts of a nonliving substance found outside the cells, called the extracellular matrix.
🔹 What Is the Extracellular Matrix?
The extracellular matrix is the non-living material found outside the cells in connective tissue.
It’s what makes connective tissue so unique compared to other tissue types like muscle or epithelial tissue.
The extracellular matrix is made up of something called ground substance and fibers.
The ground substance is structureless
✅ The Matrix Has Two Main Parts:
1. Ground Substance
It’s the background material — kind of like jelly or fluid that fills the space around the cells.
It’s made of:
Water
Cell adhesion proteins (they work like glue that helps cells stick to fibers)
Charged polysaccharides (long, sugar-like molecules that trap water)
🧠 Think of the ground substance as the gel base of the matrix.
- Fibers
These give the tissue strength, elasticity, or support.
There are 3 main types:
Collagen fibers: Strong and tough (like ropes)
Elastic fibers: Stretchy (like rubber bands)
Reticular fibers: Fine and delicate (like nets)
🔍 What Do the Polysaccharides Do?
These large, charged molecules attract and trap water, making the ground substance thicker.
The more of these molecules there are, the firmer the tissue becomes:
💧 A little = watery matrix (like blood)
🧼 More = gel-like (like cartilage)
🪨 A lot = hard (like bone)
The word “reticular” comes from the Latin word reticulum, which means “net” or “network.”
Reticular fibers are very fine collagen fibers that support soft organs by forming an internal framework. All connective tissue fibers are made from monomers produced by connective tissue cells. These monomers are released into the ground substance, where they assemble into fibers.
the diffrent things connective tissues could do because of extracellular matrix
Because the extracellular matrix in connective tissue can vary so much — from soft and squishy to firm and hard — connective tissues can do things that other tissue types can’t.
For example, they can:
Cushion and protect organs (like fat tissue)
Support weight (like bone)
Stretch without tearing (like tendons and ligaments)
Handle abrasion and pressure (like cartilage in joints)
Types of Connective Tissue
As noted previously, all connective tissues consist of living cells surrounded by extracellular matrix. Their major differences reflect specific cell types, fiber types, and the number of fibers in the matrix. At one extreme, bone and cartilage have very few cells and large amounts of hard matrix, which makes them extremely strong. At the opposite extreme, fat tissue is composed mostly of cells, and the matrix is soft. From most rigid to softest or most fluid, the major connective tissue classes are bone, cartilage, dense connective tissue, loose connective tissue, and blood. Find the various types of connective tissues in Figure 3.19 as you read the following descriptions.
Bone
Bone, sometimes called osseous (os′e-us) tissue, is composed of osteocytes (os′te-o-sītz; bone cells) sitting in cavities called lacunae (lah-ku′ne; “pits”). These pits are surrounded by layers of a very hard matrix that contains calcium salts in addition to large numbers of collagen fibers (Figure 3.19a). Because of its rocklike hardness, bone has an exceptional ability to protect and support other body organs (for example, the skull protects the brain). (We consider bone in detail in Chapter 5.)
Cartilage
Cartilage is less hard and more flexible than bone. Its major cell type is chondrocytes (cartilage cells). It is found in only a few places in the body. Most widespread is hyaline (hi′ah-lin) cartilage, which has abundant collagen fibers hidden by a rubbery matrix with a glassy (hyalin = glass), blue-white appearance (Figure 3.19b). It forms the trachea, or windpipe, attaches the ribs to the breastbone, and covers bone ends at joints. The skeleton of a fetus is made largely of hyaline cartilage; but by the time the baby is born, most of that cartilage has been replaced by bone. The exceptions include the epiphyseal, or growth, plates in long bones, which allow the bones to grow in length.Although hyaline cartilage is the most abundant type of cartilage in the body, there are others. Highly compressible fibrocartilage forms the cushionlike disks between the vertebrae of the spinal column (Figure 3.19c). Elastic cartilage is found in structures with elasticity, such as the external ear. (Elastic cartilage is not illustrated in Figure 3.19.)
Dense Connective Tissue
✅ Summary of the 3 Types of Cartilage:
1. Hyaline Cartilage – Most common
Appearance: Smooth, glassy, bluish-white
Function: Supports and cushions with some flexibility
Where it’s found:
Trachea
Ends of bones at joints
Rib–sternum connections
Fetal skeleton
Growth plates in long bones
- Fibrocartilage – Strongest and most compressible
Appearance: Thick, visible collagen fibers
Function: Shock absorber, resists compression
Where it’s found:
Intervertebral discs (between vertebrae)
Menisci in the knee
Pubic symphysis
- Elastic Cartilage – Most flexible
Appearance: Similar to hyaline but with many elastic fibers
Function: Maintains shape but allows for flexibility
Where it’s found:
External ear
Epiglottis (in the throat — helps with swallowing)
why is densce tissue not as hard as bone
Bone is hard because its extracellular matrix contains calcium phosphate and other minerals in addition to collagen. These minerals make the matrix rigid and rock-like.
Dense connective tissue has no mineral deposits. It’s made mostly of collagen fibers, which are strong and flexible, but not hard like bone.
loose connective tissue
Relatively speaking, loose connective tissues are softer and have more cells and fewer fibers than any other connective tissue type except blood. There are three main types of loose connective tissue: areolar, adipose, and reticular.
Areolar (ah-re′o-lar) connective tissue,
Areolar (ah-re′o-lar) connective tissue, the most widely distributed connective tissue variety in the body, is a soft, pliable, “cobwebby” tissue that cushions and protects the body organs it wraps (Figure 3.19e). It functions as a universal packing tissue and connective tissue “glue” because it helps to hold the internal organs together and in their proper positions. A soft layer of areolar connective tissue called the
lamina propria (lă′mĭ-nah pro′pre-ah) underlies all mucous membranes. Its fluid matrix contains all types of fibers, which form a loose network. In fact, when viewed through a microscope, most of the matrix appears to be empty space, which explains the name of this tissue type (areola = small open space). Because of its loose and fluid nature, areolar connective tissue provides a reservoir of water and salts for the surrounding tissues, and essentially all body cells obtain their nutrients from and release their wastes into this “tissue fluid.” When a body region is inflamed, the local areolar tissue soaks up the excess fluid like a sponge, and the area swells and becomes puffy, a condition called edema (eh-de′mah). Many types of phagocytes wander through this tissue, scavenging for bacteria, dead cells, and other debris, which they destroy.
adipose loose conective tissue
What It Is:
A type of loose connective tissue.
Basically, it’s areolar tissue that has been taken over by fat cells (adipocytes).
Each fat cell has a large oil droplet that:
Pushes the nucleus to the side
Takes up almost all the space in the cell
Where You’ll Find Adipose Tissue:
Under the skin (subcutaneous fat)
Around kidneys
Behind the eyeballs
Stored in areas like hips, breasts, belly
Adipose tissue = fat storage + insulation + padding
Made of fat-storing cells
Found under skin and around organs
Protects, warms, and stores energy
Reticular connective tissue
Structure:
Made of reticular fibers, which are:
Thin, delicate collagen fibers
Arranged in a net-like mesh
Contains reticular cells, which are similar to fibroblasts (the cells that build fibers).
🛏️ Function:
Forms a soft internal framework called a stroma (means “bed” or “support platform”).
This stroma supports many free blood cells, especially white blood cells (lymphocytes).
📍 Where It’s Found:
Only in certain organs that handle a lot of blood or immune activity:
Lymph nodes
Spleen
Bone marrow
Blood
Blood, or vascular tissue, is considered a connective tissue because it consists of blood cells surrounded by a nonliving, fluid matrix called blood plasma (Figure 3.19h). The “fibers” of blood are soluble proteins that become visible only during blood clotting. Still, blood is quite atypical as connective tissues go. Blood is the transport vehicle for the cardiovascular system, carrying nutrients, wastes, respiratory gases, white blood cells, and many other substances throughout the body. (We consider blood in detail in Chapter 10.)
