Connective Tissue
Stefanie Schutz, Paula Bang, Chandler Hicks
Dept. of Biology, Trinity University
Connective Tissue Proper
Introduction
The human body can be compartmentalized into various
differently functioning areas, or organs, and it is the connective
tissue that connects and mediates the communication between
them. Connective tissue provides support, cohesion, and strength
to the involved organs. Connective tissue is comprised of cells,
fibers, and matrix. First, the three types of cells found in the
connective tissue are blasts, cytes, and clasts. Blasts create the
matrix, cytes maintain it, and clasts break it down. Cells could also
be classified into two types – resident cells, and wandering cells.
Fibroblasts, macrophages, mesenchymal cells, and reticular cells
are resident cells. In contrast, plasma cells, mast cells, leukocytes,
and pigment cells are examples of visiting cells. Second, the three
types of fibers are collagenous, reticular, and elastic. Finally, the
matrix is made up of water, salts, glycoproteins, proteoglycans, and
glycosaminoglycans (GAGs). Connective tissue could be categorized
into three distinct groups – embryonic, proper, and specialized.
They differ in the proportion and types of cells, fibers, and matrix.
Embryonic Connective Tissue
The two types of embryonic connective tissue are embryonic mesenchyme
and embryonic mucoid membrane. The mesenchyme is derived from
various spots in the mesoderm in the very young embryo. It is an
undifferentiated loose connective tissue which can also be found in adults.
The mesenchymal cells can migrate into different places of body and
develop into differentiated cells. The mucoid tissue is slightly more
differentiated than the mesenchyme and is made up of mainly matrix. It is
found during fetal development and supports the blood vessels of umbilical
cord.
Figure 1. Mesenchymal
Embryonic. This shows a very
loose tissue with no cells that
have an obvious purpose.
These cells are waiting to
differentiate into an adult cell.
Mescher. X200.
Connective Tissue Proper
Loose Connective Tissue
Loose connective tissue shown here tends to be equal parts cells, fibers
and ground substance with the most common cell being fibroblasts. Loose
connective tissue tends to be vascularized by the an extensive blood vessel
network. The main function of loose connective tissue is support for
epithelium and the most idealized example is the lamina propria of the
epithelium of the digestive tract. It also is found between muscle cells and
nerve cells, and provides immune cells with a beneficial environment.
Loose connective tissue is exactly what its’ name suggests, it is not tightly
woven and does not have a high resistance to stress.
Figure 2. Loose
Connective Tissue.
This figure shows a
very fibrous tissue
with the darker spots
representing
fibroblasts and the
white space being
ground substance.
Mescher.x100.
RESEARCH POSTER PRESENTATION DESIGN © 2012
www.PosterPresentations.com
Specialized
Connective
Specialized
Connective
TissueTissue
Dense Connective Tissue
Figure 3. Dense Regular
Connective Tissue. This
figure shows the long
dense collagenous
fivers and the dark
areas represent
fibroblasts in a tendon
(20x).
There are two types of Dense Connective issue: Regular and Irregular.
Irregular connective tissues’ composition is mostly collagen, and it forms
thicker layers than loose connective tissue due to collagen bundles.
Dense regular connective tissue is recognizable because it is mostly
collagen with few fibroblasts. Its most important function is providing
strong musculoskeletal connections, and the most common example is a
tendon or a ligament. Both regular and irregular provide protection.
Specialized Connective Tissue
Adipose Tissue
Bone
Bone is a type of connective tissue with a calcified extracellular
matrix (ECM). The functions of bone are to provide support,
protect internal organs, and act as the body’s Ca2+ reservoir.
The three major cell types of bone are osteoblasts, osteocytes,
and osteoclasts. These cells types make up two types of bone:
woven and lamellar bone (compact bone 80% and cancellous
bone 20%).
Reticular Tissue
Adipose is characterized by adipocytes, or fat cells. Adipose represents 15%20% of the body weight, on average. White Adipose tissue is said to be
unilocular because the fat is stored in a large droplet where in brown
adipose tissue is characterized by its’ numerous smaller fat droplets and
abundant mitochondria. Brown adipose is known for thermogenesis and
white is known for storage and metabolic activity.
.
Reticular tissue is a network of collagen, fibroblast, and reticulin.
Reticular tissues major function is support, especially for bloodforming and secretory cells. Reticular tissue is known for creating
and supporting microenvironments conducive to hematopoiesis.
Phagocytic cells such a macrophages are also found in the reticular
tissue and catch things entering and leaving the blood that are not
supposed to be there.
Figure 8. Bone. Osteons (Haversian systems) constitute most of the compact
bone. Transverse perorating canals connecting adjacent osteons. Such canals
“perforate” lamellae and provide another source of microvasculature for he
central canals of osteons. x40
Lymphatic
Figure 4. Adipose Tissue. The large white spaces are where the lipid
droplet is stored, and the small dark nuclei lay along the circumference
are unique to adipose. X100.
Blood
Blood is a form of connective tissue where the cells
are suspended in an extracellular matrix of plasma.
The elements in the plasma include erythrocytes,
leukocytes, and platelets. The many functions of
blood include: distribution and transportation of O2
and CO2, metabolites, hormones, and heat.
Figure 5. Reticular Tissue. The collagen fibers are very apparent in
the reticular, and the darker small dots represent fibroblast. x100.
Cartilage
Cartilage is a tough, flexible form of connective tissue, which has a
prominent extracellular matrix (ECM). The interaction of the ECM with
collagen and elastic fibers allows it to bear considerable stress
without permanent distortion. There are three types of cartilage:
hyaline, elastic, and fibrocartilage. The three types of cartilage are
made of cells called chondrocytes and are avascular. The differences
in cartilage type reside in the composition of the matrix components
and cells produced.
Lymphatic tissue is a form of reticular connective tissue in the
lymphatic system that contains many lymphocytes. Lymphatic
tissue can be found in the thymus, bone marrow, spleen, gastrointestinal tract, visceral nodes, lacteals, and Peyer’s patches. The
function of the tissue is to drain interstitial fluid, transport dietary
lipids, and protect the body from invasion and infection.
Figure 9. Lymphatic Tissue. Lymphatics converge into large, thin-walled
lymphatic vessels in which lymph is propelled by movements of
surrounding muscles and organs, with intimal valves keeping the flow
unidirectional. Magnification Unknown. VetMed.
References
1. http://www.physioweb.org/tissues/connective.html
Figure 6. Blood. This figure shows a typical sampling of blood
from a blood smear, you can see the shape and multitude of
erythrocytes. It also highlights the red blood cell to white blood
cell count ratio. x40.
Figure 7. Types of Cartilage. Hyaline cartilage is known for its large
lacunae and lack of fibers. Fibrocartilage has many collagenous fibers,
and Elastic is known for its abundance of elastin fibers. Mescher.
2. Mescher, A.L. (2013) Junqueira’s basic histology text & atlas. 13th
ed. Singapore. The McGraw Hill Companies.
3. http://en.wikipedia.org/wiki/Mesenchyme
4. http://medicaldictionary.thefreedictionary.com/mucous+connective+tissue
5. http://www.vetmed.vt.edu/education/curriculum/vm8054/Labs/L
ab13/Lab13.htm