Anatomy

Tissues of body

M Humayun jamil

7/5/2014

Tissues Tissue – group or layers of similar type of cells performing a common function.

Examples – epithelial, connective tissue

Epithelial tissuesEpithelial 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

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.

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.

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.

Stratified EpitheliaStratified 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

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 epitheliumwithout 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.

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

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 glandsas 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 TISSUEConnective 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).

Osteoblasts 

secrete matrix in bone to help create bone.

Blood cells don’t produce matrix.  In blood, the ECM is plasma.

Fat cells, white 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

from gel-like to hard in texture) and protein fibers (collagen, reticular, elastic).  It provides cushioning and protection such as the

kidneys, which are surrounded by fat.

Protein fibers such as…

Collagen fibers:

 very strong, comparable to iron or steel but they are very tiny.  These are the thickest and strongest of the 3 fibers.

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 filter.

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 soft and gel like with 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 where so many of our defenses wait.  Macrophages, mast cells and

white blood cells gather here.  It wraps and cushions organs and is widely distributed under epithelia of the body.  This contains all 3

fiber types in its matrix secreted by fibroblasts.

3. Adipose (fat) tissue

are required to protect your organs and help maintain your body temperature.  For example, lots of this is found in woman’s breasts

and under our skin.

4. Reticular connective tissue

forms the soft internal skeleton of something.  The spleen and lymphoid organs for example, is full of these because it acts like a

filter that catches all sorts of things.

Three types of dense connective tissue

1.. Dense regular connective tissues

 attaches muscle to bone and with 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 fibers, a few elastic fibers and the major cell type is the fibroblast.

2. Dense irregular connective tissue

 are like capsules for organs and joints that wrap around them.  Irregular allows for movement in different directions, like

the shoulder or under the skin or the fibrous capsule of an organ or joint. It’s made primarily of irregularly arranged collagen fibers,

some elastic and the major cell type is the fibroblast.

3. Elastic connective tissue 

has the ability to receive a relatively large amount of blood all at once with a lot of pressure.  The aorta for example has to expand

and recoil RIGHT AWAY because the next heart beat is on the way.  It’s just like a dense regular connective tissue but with a high

proportion of elastic fibers instead

Connective tissue properit has loose flexible matrix that is mostly called ground subctance

Firoblastthese are most common cells of CTP that are large, star shaped cells and produce collagenous ,elastic and reticular fibers.

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

CartilageIt 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 cartlilageIt is of three types

1. Hyaline cartilage2. Fibrocartilage3. Elastic cartilage

Hyaline cartilage:-

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 LocationHyaline 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

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

BoneIt 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

1. Bone forming cells/ osteoblastss2. Bone cells found in cavities called lacuna/ osteocalsts3. Cells that respond to trauma or fractures/ osteogenic

Types;-

1. Spongy bones2. 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 bones1. Long bones2. Short bones3. Flat bones4. Irregular bones

Long bonesThese 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 bonesThey 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

They have varied shapes and have many surface features for muscle attachment

e.g bones of vertebra and certain bones of skull

In case of any mistake please inform me at my email address

However typing errors are possible

Humayunjamil4@gmail.com

Thankx