2. Tissues
Tissue – group or layers of similar type of cells performing a common function.
Examples – epithelial, connective tissue
Epithelial tissues
Epithelial tissues that are composed of a single layer of cells are called simple; those that are layered are
said to be stratified.
Squamous cells are flattened; cuboidal cells are cube- shaped; and columnar cells are taller than they
are wide.
Simple Epithelia
3. Simple epithelial tissue is a single cell layer thick and is located where diffusion, absorption, filtration,
and secretion are principal functions. The cells of simple epithelial tissue range from thin, flattened cells
to tall, columnar cells. Some of these cells have cilia that create currents for the movement of materials
across cell surfaces. Others have microvilli that increase the surface area for absorption.
Simple Squamous Epithelium
Simple squamous epithelium is composed of flat- tened, irregularly shaped cells that are tightly bound
together in a mosaic like patter. Each cell contains an oval or spherical central nucleus It occurs in the
pulmonary alveoli within the lungs ,in portions of the kidney , on the inside walls of blood vessels, in the
lining of body cavities, and in the covering of the viscera. The simple squamous epithelium lining the
inner walls of blood and lymphatic vessels is termed endothelium . That which covers visceral organs
and lines body cav- ities is called mesothelium .it functions diffusion and filtration
Simple Cuboidal Epithelium
Simple cuboidal epithelium is composed of a single layer of tightly fitted cube-shaped cells.This type of
epithelium is found lining small ducts and tubules that have excretory, se- cretory, or absorptive
functions. It occurs on the surface of the ovaries, forms a portion of the tubules within the kidney, and
lines the ducts of the salivary glands and pancreas.
4. Simple Columnar Epithelium
Simple columnar epithelium is composed of tall, columnar cells .Each cell contains a single nucleus
which is usually located near the basement membrane.
5. Simple Ciliated Columnar Epithelium
Simple ciliated columnar epithelium is characterized by the pres- ence of cilia along its free surface . By
contrast, the simple columnar type is unciliated. Cilia produce wavelike movements that transport
materials through tubes. This type of epithelium occurs in the female uterine tubes to move the ovum
(egg cell) toward the uterus.
6. Stratified Epithelia
Stratified epithelia have two or more layers of cells. They are classified according to the shape of the
surface layer of cells
Stratified Squamous Epithelium
Stratified squamous epithelium is composed of a variable number of cell layers that are flattest at the
surface. Mitosis occurs only at the deepest layers
7. There are two types of stratified squamous epithelial tis- sues:
Keratinized
nonkeratinized.
1. Keratinized stratified squamous epithelium
contains ker- atin, a protein that strengthens the tissue. Keratin makes the epidermis (outer
layer) of the skin somewhat waterproof and protects it from bacterial invasion.
2. Nonkeratinized stratified squamous epithelium
without the surface layer of dead cells.lines the oral cavity and pharynx, nasal cavity, vagina,
and anal canal. Resists abrasion and penetration by pathogenic organisms
Stratified Cuboidal Epithelium
Stratified cuboidal epithelium usually consists of only two or three layers of cuboidal cells This type of
epithelium is confined to the linings of the large ducts of sweat glands, salivary glands, and the pancreas,
where its stratification probably pro- vides a more robust lining than would simple epithelium.
8. Glandular Epithelia
These glands remain connected to the epithelium by ducts, and their secretions pass through the ducts
onto body surfaces or into body cavities. Exocrine glands should not be confused with en- docrine
glands, which are ductless, and which secrete their prod- ucts (hormones) into the blood or surrounding
extracellular fluid. Exocrine glands within the skin include oil (sebaceous) glands, sweat glands, and
mammary glands. Exocrine glands within the digestive system include the salivary and pancreatic glands.
Exocrine glands are classified according to their structure and how they discharge their products.
Classified according to structure
there are two types of exocrine glands
unicellular and multicellular glands.
1. Unicellular glands
9. are single-celled glands, such as goblet cells. They are modified columnar cells that occur within
most epithelial tissues. Goblet cells are found in the epithelial linings of the respiratory and
digestive sys- tems. The mucus secretion of these cells lubricates and proects surface lining
2. Multicellular glands
as their name implies, are composed of both secretory cells and cells that form the walls of the
ducts.
Multicellular glands are classified as simple or compound glands. The ducts of the simple glands do
not branch, whereas those of the compound type do
1. Merocrine glands are those that secrete a wa- tery substance through the cell membrane of the
secretory cells. Salivary glands, pancreatic glands, and certain sweat glands are of this type.
2. Apocrine glands are those in which the secre- tion accumulates on the surface of the secretory cell;
then, a portion of the cell, along with the secretion, is pinched off to be discharged. Mammary glands
are of this type.
3. Holocrine glands are those in which the entire secretory cell is discharged, along with the secretory
prod- uct. An example of a holocrine gland is an oil -secreting (sebaceous) gland of the skin
CONNECTIVE TISSUE
Connective tissue is the most abundant tissue in the body. It sup- ports other tissues or binds them
together.connective tissue is highly vascular and well nourished. It is able to replicate.Connective tissue
does not occur on free surfaces of body cavities or on the surface of the body, as does epithelial tissue.
Furthermore, connective tissue is embryonically derived from mesoderm, whereas epithelial tissue
derives from ectoderm, mesoderm, and endoderm.
Main classes of connective tissue
Connective tissue proper
Cartilage
Bone
Blood
Cells in Connective Tissue (mostly secrete ECM)
Fibroblasts
are cells in connective tissue that make fibrous proteins and secrete the molecules that form ground substances and
collagen.
Chondroblasts
secrete matrix in cartilage (to make chondrocytes).
10. Osteoblasts
secrete matrix in bone to help create bone.
Blood cells don’t produce matrix. In blood, the ECM is plasma.
Fat cells, w hite blood cells and mast cells may also be present in connective tissue.
Structural Elements of Connective Tissue
Extracellular Matrix
Ground substance that has a lot of sugar-proteins and large sugars. Extracellular matrix is composed of ground substance (ranges
f rom gel-like to hard in texture) and protein f ibers (collagen, reticular, elastic). It provides cushioning and protection such as the
kidneys, w hich are surrounded by fat.
Prote in fibers s uch as…
Collagen fibers:
very strong, comparable to iron or steel but they are very tiny. These are the thickest and strongest of the 3 f ibers.
Reticular fibers
are found in organs that have lots of mesh-like internal structure. The spleen for example is full of these because it acts like a f ilter.
Elastic fibers
stretch and recoil and contain a rubberlike protein called elastin.
Classification of connective tissues
Loose connective tissue (areolar, adipose and reticular)
Dense connective tissue (regular, irregular, elastic)
Three types of loose connective tissue
Areolar connective tissue
is sof t and gel like w ith some elasticity and holds interstitial fluid which carries and delivers nutrients or waste. It helps facilitate
the passage of these molecules for the most part. This is also w here so many of our defenses wait. Macrophages, mast cells and
w hite blood cells gather here. It w raps and cushions organs and is w idely distributed under epithelia of the body. This contains all 3
f iber types in its matrix secreted by f ibroblasts.
11. 3. Adipose (fat) tissue
are required to protect your organs and help maintain your body temperature. For example, lots of this is f ound in w oman’s breasts
and under our skin.
4. Reticular connective tissue
forms the sof t internal skeleton of something. The spleen and lymphoid organs for example, is full of these because it acts like a
f ilter that catches all sorts of things.
Three types of dense connective tissue
1.. Dense regular connective tissues
attaches muscle to bone and w ith the cells organized in one direction so that it pulls in one direction, like a tendon that connects to
the bicep. It is made primarily of parallel collagen f ibers, a few elastic f ibers and the major cell type is the f ibroblast.
2. Dense irregular connective tissue
are like capsules for organs and joints that w rap around them. Irregular allow s for movement in dif ferent directions, like
the shoulder or under the skin or the f ibrous capsule of an organ or joint. It’s made primarily of irregularly arranged collagen f ibers,
some elastic and the major cell type is the f ibroblast.
3. Elastic connective tissue
has the ability to receive a relatively large amount of blood all at once w ith a lot of pressure. The aorta for example has to expand
and recoil RIGHT AWAY because the next heart beat is on the w ay. It’s just like a dense regular connective tissue but w ith a high
proportion of elastic f ibers instead
Connective tissue proper
it has loose flexible matrix that is mostly called ground subctance
Firoblast
these are most common cells of CTP that are large, star shaped cells and produce collagenous ,elastic
and reticular fibers.
12. Collagenous fibers
are made up of protein called collagen. They are flexible and have tramedous strength
Elastic fibers
are composed of protein called elastin and give elasticity to certain tissues
These both fibers may be irregularly arranged as in loose connective tissues where they generally form
packing materials that cushions different organs
But they may be tightly packed as in dense connective tissues where they form binding and supportive
functions of body
Reticular fibers
are joined together to form reticulum. These are found in lymphatic vessels
Cartilage
It Consist of crtilage cells / chondrocytes and semisolid metrix that imparts elastic properties to tisseues
These chondrocytes are sometimes singular but mostly clustered
Cartilage is free of blood vessels
Functions of cartilage;
It provides support and protection to bones
It gives shape to outer ear, auditory canal, parts of larynx, tip of nose etc
Types of cartlilage
It is of three types
1. Hyaline cartilage
2. Fibrocartilage
3. Elastic cartilage
Hyaline cartilage:-
13. It is named so because of its clear glassy appearance that is due to fineness of its collagen fibers. It has
homogeneous bluish staining matrix. Its collagen fibers are so much fine that they can be seen only
under electron microscope. These are most abundant cartilage in human body
These are located in articular surface of bone, nose, walls of respiratory track, fetal skelton, portions of
rib cage etc
It provides flexible support to bones. It also provides protection to bones. It is precursor of bones
Fibrocartilage;-
It is named so due to its coarse readily visible bundles of collagen. Its matrix has abundant collagen
fibers
These are located in knee joints,intervertaberal discs and symphasis pubis
Its function is to withstand compression
Elastic cartilage
It is named so because of its elastic fibers. It is similar to hyaline cartilage except presence of abundant
elastic fibers. It is yellowish in appearance
It is located in outer ear, auditory canal and parts of larynx
Its function is to provide flexibilitry to bones
Summary of Cartilage
Type Structure and Function Location
Hyaline
cartilage
Homogeneous matrix with extremely fine
collagenous fibers; provides flexible support,
protects, is precursor to bone
Articular surfaces of bones, nose, walls of
respiratory passages, fetal skeleton
Fibrocartilage Abundant collagenous fibers within matrix;
supports, withstands compression
Symphysis pubis, intervertebral discs, knee
joint
Elastic
cartilage
Abundant elastic fibers within matrix;
supports, provides flexibility
Framework of outer ear, auditory canal,
portions of larynx
14.
15. Muscle tissue:
very specialized to produce movement, maintain posture; muscle cells contain large number of
contractile proteins; can not reproduce three types of muscle - skeletal, cardiac and smooth
Bone
It is composed of bone tissues/ osseous tissues. Bone tissues have rich vascular supply and it is the site
of considreable metabolic activity. Bones hardness is due to calcium and phosphate. Bone matrix has
many collagen fibers embeded in it that give it flexibility. Outer surface of bone is covered by type of
loose connective tissue called periosteum that provides site of attachement for tendens and ligaments,
provides protection and durable strength to bones
Bone cells;
Bone has three type of cells
16. 1. Bone forming cells/ osteoblastss
2. Bone cells found in cavities called lacuna/ osteocalsts
3. Cells that respond to trauma or fractures/ osteogenic
Types;-
1. Spongy bones
2. Compact bones
Spongy bones;
Spongy bone tissue constitute porus highly vascular inner portions. These are present in heads of long
bones. It has calcified, spongy appearance. It is always covered by compact bones
It is lighter due to its spongy bone tissues. It provides space for red bone marrow where RBCs are
formed
Compact bones;
Compact bone tissue constitute compact bone. In compact bone mature bone cells called osteocytes are
arranged in concentric layers around a centeral canal which contains vascular and nerve supply.
Each osteocyte occupies a cavity called lacuna. Radiating from each lacuna are numerous minute
mineral canals or canaliculi. Nutrients diffuse through these canaliculi to reach other osteocytes. The
matrix is arranged in concentric layers called lamella. It is more dense.
Types of bones
1. Long bones
2. Short bones
3. Flat bones
4. Irregular bones
Long bones
These are longer bones and function as liver e.g femur tibia,radius,ulnas,metacarpals,metatarsals
Short bones
These are cube shaped, located in wrist and ankelwhere they transfer force of movement e.g cuboidal
bone
Flat bones
They have broad surface for muscle attachement e.g cranial bones, rib bones and bones of shoulder
griddle
nective tissue or Wharton’s jelly. It gives a turgid consis- tency to the umbilical cord.
Irregular bones
17. They have varied shapes and have many surface features for muscle attachment
e.g bones of vertebra and certain bones of skull
18.
19. In case of any mistake please
inform me at my email address
However typing errors are
possible
Humayunjamil4@gmail.com
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