How many types of tissues do you know ? What are tissues
composed of ?Do you know their functions ?
four main types of tissues in our body
1. epithelial tissues : cover and protect our body surfaces
2. connective tissues : support and binding, protection of
the organs
3. muscle tissues : force and movement generation
4. nervous tissues : communication and control
EPITHELIAL TISSUES
Epithelium is a thin layer of tightly packed cells that covers and protects surfaces,
both inside and outside the body.
where can we find the epithelium ?
function of an epithelium can be diverse depending on the location
and organs that it can be found
1. protection ( like the epithelium lining the skin )
2. absorption ( like intestinal linings absorbing nutrients )
3. secretion ( like glands secreting mucous or sweat )
4. sensation ( like epithelium of your tongue sensing taste )
do you think all epithelium looks the same ? Refer to the pictures in
page 2 .
epithelial classification according to their layers
1. simple epithelium : single layer
2. stratified epithelium : multiple layers
3. pseudostratified epithelium : looks like it has multiple layers but actually
has one layer with the nuclei at different heights
Now lets study the infrastructure close up view of epithelial tissues
since they are tissues, they are composed of many cells. The cells in
epithelial tissues are tightly packed to each other. They have little or
no gaps or spaces between one cell and another. This tight
arrangement is reinforced by cellular junctions such as desmosomes.
Cells are polarized, meaning that they can be distinguished into
apical surface and basal surface which is attached to underlying
tissue .
cells dont have the vascularizations, no blood vessels , they receive
nutrients by diffusion from the underlying tissues below
classifications of epithelium according to the cell shape
1. squamous : thin, flat cells
2. cuboidal shape : cube shaped cells
3. columnar shape: tall , column like cells
types of epithelium combining both shapes and layers
transitional epithelium
Transitional epithelium is a special type of stratified epithelium that is highly stretchable.
It is found in organs that expand and contract, like the urinary bladder, ureters, and urethra.
The cells change shape depending on how much the organ is stretched.
Cell Shape in Different Conditions:
Relaxed State (Empty Bladder) → Cells appear rounded/dome-shaped.
Stretched State (Full Bladder) → Cells become flattened/squamous-like.
Think of it like an accordion! When no urine is present, the tissue is thick and folded, but as urine accumulates, it stretches and thins out.
specialized projections on the epithelium
1. microvilli : tiny finger like projections on the cell surface.
Purpose is to increase the surface area for absorption .
found in areas like small intestines.
2. cilia : hair like extensions move in a coordinated way . found in
trachea and bronchi to remove the dust particles and mucous +
fallopian tubes to move egg towards the uterus
3. goblet cells ( they are not projections , but important structures )
specialized cells embedded within the epithelium and secretes
mucus . it protects and lubricates surfaces .
2. connective tissues
Connective tissue is one of the four main tissue types in the body. It supports, binds, and protects
organs while also playing roles in transport, storage, and immune defense.
Characteristics of Connective Tissue
✔ Cells are widely spaced (unlike epithelium, where cells are tightly packed).
✔ Has an extracellular matrix (ECM) made of fibers + ground substance.
✔ Mostly vascular (except cartilage, which has no blood supply).
✔ Derived from mesoderm (embryonic tissue).
loose areolar connective tissue
loose : the fibers are loosely arranged , not tightly packed like in the dense
connective tissue
areolar : derived from a latin word areola: meaning small open space , it is
because the tissue has a lot of space between fibers
it is a soft , flexible tissue with open spaces like a sponge, that holds and
supports structures
dense connective tissue
dense : fibers are very dense, making the tissue strong and resistant to
stretching
it is strong , sturdy like a thick rope, able to handle tension
we have dense regular CT and dense irregular CT
dense regular : fibers are parallel, in one direction like a neat bundle of
ropes . found in tendons and ligaments
dense irregular : fibers are in multiple directions and crisscross , found
in dermis
cartilage connetive tissue
strong, flexible connective tissue for support and cushioning . it is
softer than bones but stronger tha regular connective tissue .
cartilages are slow to be healed because they have no vascularizations.
they depend on nutrients diffusion.
cells of the cartilages are called chondrocytes . there are found in spaces
called lacunae. The matrix is made up of collagen and elastic fibers .
how many types of catilages have you heard of before ?
1. hyaline cartilage : nose tips - made up of a few collagen fibers and
elastic fibers
2. elastic cartilage : external ears( pinnae ) : a lot of elatic fibers
3. fibro cartilage: intervertebral discs : a lot of collagen fibers
bone connective tissues
cells : three types
Osteoblasts → Bone-forming cells (build new bone).
Osteocytes → Mature bone cells, maintain bone structure.
Osteoclasts → Bone-destroying cells (help in bone remodeling).
matrixes : two types
Two types of matrixes- organic matrix (made up of protein fibers)
-inorganic matrix(made up of mineral salts( calcium salts) )
Organic matrix makes bone flexible. Inorganic matrix provides hardness.
Inadequate organic matrix=the bone will break.
Inadequate inorganic matrix= the bone will bend.
types of bone tissues : two
a
sponse
&
compact bone : dense, strong and found in the outer layer of bones. in
long bones, compact bones are found in the diaphysis ( shafts )
spongy bone : porous , lightweight inner layer of bones . in long bones,
they are found in the epiphysis of the long bones
structure of a compact bone
kunal
since
-
structure of a spongy bone
osteen
.
Trabeculae are needle-like, interconnected bony structures in spongy
bone that provide lightweight strength and house red bone marrow for
blood cell production.
Adipose connective tissue
blood connective tissue
Definition:
Blood is a fluid connective tissue that transports oxygen, nutrients, hormones, and waste throughout the body.
Cells:
•
Red Blood Cells (Erythrocytes) → Carry oxygen via hemoglobin.
•
White Blood Cells (Leukocytes) → Fight infections (e.g., neutrophils, lymphocytes).
•
Platelets (Thrombocytes) → Help in blood clotting.
✔ Fibers: None in normal blood (fibrin appears only during clotting).
✔ Ground matrix: Plasma (90% water, contains proteins, hormone
end of lecture exercises
Which type of epithelium is best suited for rapid diffusion of gases?
(A) Stratified squamous
(B) Simple squamous
(C) Pseudostratified columnar
(D) Transitional
Which of the following statements about transitional epithelium is TRUE?
(A) It is only found in the respiratory tract.
(B) It contains cilia to move mucus.
(C) It allows organs to stretch and return to their shape.
(D) It is composed of a single layer of cells.
Which component of blood connective tissue is responsible for clotting?
(A) Red blood cells
(B) White blood cells
(C) Platelets
(D) Plasma
Where is spongy bone mainly found in long bones?
(A) In the diaphysis
(B) In the periosteum
(C) In the epiphysis
(D) In the central canal of osteons
Which of the following correctly describes the role of osteoblasts?
(A) They break down bone tissue.
(B) They are responsible for forming new bone.
(C) They store fat in the bone marrow.
(D) They transport oxygen in bone tissue.
What makes cartilage different from other connective tissues?
(A) It has a rich blood supply.
(B) It contains large amounts of nerve endings.
(C) It lacks blood vessels and heals slowly.
(D) It is only composed of elastic fibers.