cell and tissues rebat uni

© Dr. Yahia Fadl Tahir. Zoology and Human Biology - 1st Year. National Rebat University, Faculty of Pharmacy -2013

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ZOOLOGY AND HUMAN BIOLOGY

1-Introduction

Origin of life

Scientists of Astronomy hypothesize that the cosmos had been formed before 10-20

billion years ago. While the solar system originated before 5-4.5 billion years ago,

during which the earth created from the sun when it was condensing as a result of

centrifuge of hot materials of clouds, dusts and gases. The earth detached as other planets

did from the sun. The atmosphere of the earth contained high percentage of hydrogen and

the temperature was very high, which would have promoted the combination of some

available elements. In this way there could have arisen ammonia, methane and water

vapour. These materials believed to have been the first constituents of the earth

atmosphere.

Before 4 billion years life was originated and this is recorded in rocks as fossils. The first

living organism was the bacteria. The hypothesis of life origin is that: in presence of

nitrogen, ammonia, methane and water vapour in a such reducing condition and sparks of

electric shocks which nowadays comes from Jupiter and in presence of ultraviolet as a

source of energy (at that time the ozone was not formed). This hypothesis was

experimented by Miller (1952-1954) when he passed electric discharge through the

mixture of nitrogen, ammonia, methane and water vapour, as a result the fundamental

substances required by the organism (e.g. formic acid, suiccinic acid and amino acids) or

polymers of amino acids peptide-like structures.

Before 1.5 billion years (Precambrian era) more complex organism were originated

these were fungi as well as plants. At that time the earth environment was became more

suitable for complex sort of life.

Before 600 million years the invertebrates was originated. Then vertebrates originated

mainly fishes before 500 million years and the man before 0.4 million years ago.

2-Cytology

Cell Theory

The theory is summarized in the following points:

1- The cell is the unit of life structurally and functionally.

2- Most organisms contain or consist of a large number of cells.

3- Cells have essentially the same nature and units of structure.

4- Cells arise from pre-existing cells.

5- Cells sometimes transformed into bodies no longer possessing all the character of

cells.

Protoplasm

Physical Properties:

Protoplasm is a transparence colloid emulsion substance. It has the property reversible

solution and gelatin depending on the degree of the temperature and pressure e.g. cells

division and amoeboid movement. It is surrounded by plasma membrane and includes

cellular organelles.

Chemical Composition:

Chemically, the protoplasm is composed of:

Organic substances : 9-10% of the substances are:

a- carbohydrates

b- lipids and fats

c- protein

d- nucleic acids, (RNA - deoxyribonucleic acid and DNA- ribonucleic acid)

Inorganic substances: many ions are present in the protoplasm as well as salts (sodium and

potassium chloride) and mineral e.g. calcium.


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Water: 10-90% weight of the protoplasm is water. Water is the solvent of many

substances inside and outside the cell.

3-Cell Types

Prokaryote - Eukaryote:

Table 1- Comparison between Prokartote and Eukarote cells.

Character / cell

type

Prokaryotic Eukaryotic

1-Nuclear

membrane

Absent Present

2-Nucleus Absent Present

3-Size 1-10 micron 10-100 micron

4-Cytoplasmic

movement

No cytoplasmic movement Cytoplasmic movement

(engulfment, pinoctosis)

5-DNA Naked and circular Combined protein

6-Chromosome Single Multiple

7-Cell division Amitosis (fission) Mitosis or meiosis

8-Golgi

appeatus

Absent Present

9-lysosome Absent Present

10- centriol Absent Present

11-Endoplasmic

reticulum

Absent Present

12-Mitochondria Definite organelle absent

enzymes of respiration and is

stored in folds of plasma

membrane

Present

13-Chlorplast Absent Present (in plants and )

14-Cell wall Present (noncellulosic) Present (cellulosic in

plants)

15-Flagella No definite arrangement of

fibrils

9 in outer circle and 2 in

the center

Classification of Living Organisms (Monera, Protista, Fungi, Plantae, and Animalia:

All living organisms are divided into five kingdoms: Monera, Protista, Fungi, Plantae, and

Animalia. At the cellular level, there are changes from kingdom to kingdom. Browse through

each of our kingdom profiles above to find out what makes each kingdom unique. Within cells

there is an intricate network of organelles that all have unique functions. These organelles allow

the cell to function properly. Arranged below according to location (nucleus, cytoplasm, and

surface) is a description of common organelles.

Table 2- Comparison between kingdoms of living organisms at cellular level

Character/Ki

ngdom Monera Protista Fungi Plantae Animalia

CELL

TYPE

Prokaryotic Eukaryotic

CELL

NUMBER

Unicellular or multicellular Multicellular

ATTRIBUT

ES

Genetic

material is

Many are

animal-like or

Have a cell

wall made of

Numerous

plastids

Lack cell wall

and plastids


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found in

cytoplasm

which lacks

membrane-

bound

organelles

Possess a cell

wall

Some have a

flagellum

plant-like

Some contain

chlorophyll

Flagellum may

be used for

locomotion

chitin

More than one

nucleus per

cell

Cytoplasm is

transferred

from cell to

cell (cell walls

are not sealed)

Characterist

ically large

vacuoles

Cell walls

made of

cellulose

Two main

types:

vertebrates and

invertebrates

Centrioles are

unique to

animal cells

FOOD Engulfed

from outside

sources

Produces their

own

Also captured

from outside

sources

Obtains from

outside sources

Produces

their own

Takes in

organic matter

REPRODU

CTION

Fission (a

single cell

divides into

two new

cells)

Sexual

reproduction

Sexual and

asexual

Sexual and

asexual

Sexual Sexual and

asexual

EXAMPLES Bacteria,

blue-green

algae

Paramecium,

euglena,

diatoms,

golden algae,

dinoflagellates,

green algae,

brown algae,

and red algae

Yeast,

mushrooms,

penicillin

molds, lichens,

and slime

molds

Mosses, fir

trees, and

flowering

plants

Sponges,

jellyfish,

worms,

spiders, snails,

crabs, insects,

fish, birds, and

mammals

Protista Fungi Prokaryote(Monera)


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Cell Structure and Function

The protoplasm is differentiated into two parts nucleoplasm and cytoplasm; the nucleus is

surrounded by Nuclear membrane. Plasma membrane surrounds the cytoplasm.

a- Nucleoplasm:

Chromosomes:

They are the main genetic material and present in the nucleus. Usually they are in the form

of chromatin and appear only when cell dividing. and set number per species (i.e. 23 pairs

for human)

Nuclear membrane:

Double layers membrane surrounds nucleus and controls material exchange between the

cytoplasm and the nucleus. It has selective permeability.

Nuclear sap or karyolymph: Nucleoplasm or nuclear sap is colorless solution and contains organelles. It mainly

composed of water with free-floating molecule, DNA and RNA.

Nucleolus:

Spherical in shape

Visible when cell is not dividing

Contains RNA for protein manufacture

Bar body:

It is small chromatin body near the nuclear membrane in female of animal’s nervous

tissues.

b-Cytoplasm

Centrioles:

Paired cylindrical organelles Lie at right angles to each other near nucleus.

Composed of nine tubes, each with three tubules. Involve in cellular division

and cilia movement

Chloroplasts:

A plastid usually found in plant cells

Contain green chlorophyll where photosynthesis takes place


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Cytoskeleton:

Composed of microtubules

Supports cell and provides shape

Aids movement of materials in and out of cells

Endoplasmic reticulum:

It is of two types granular or rough and agranular or smooth endoplasmic reticulum.

Rough type the ribosomes embedded in surface and present in tissues producing proteins

like liver and pancreas, while Smooth type lacks ribosomes and present in eye retina and

its function may be sensation. Stores, separates, and serves as cell's transport system

Ribosomes:

Composes 25% of cell's mass.

Stationary type: embedded in rough endoplasmic reticulum

Mobile type: injects proteins directly into cytoplasm


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Golgi apparatus:

it is a membrane structure found near nucleus. It has a fundamental role in production of

zymogene (enzymes precursor), bile, mucous, vitamin G and others.

It is very sensitive to physiological condition of the animal as vitamin D deficiency

and exposure to chemical such pesticides and phosphorous.

Lysosome:

Present in organs cell digestion occurs like liver, kidney, and small intestine. Transports

undigested material to cell membrane for removal.It is very sensitive to physiological

condition as disease (cancer) and exposure pesticides where it becomes very little in

number.

Mitochondria:

It present in most tissues and the number is constant in cells of the same type.

Double-layered outer membrane with inner folds called cristae

Energy-producing chemical reactions take place on cristae

Recycles and decomposes proteins, fats, and carbohydrates, and forms urea

It is very sensitive to physiological condition as disease and exposure pesticides cyanide,

phosphorous and x-rays where it becomes fat drops.


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Vacuoles:

Membrane-bound sacs for storage, digestion, and waste removal. they are

Osmotic pressure regulators

Cell wall:

Most commonly found in plant cells (cellulose) and in fungi (chitin).

Controls turgity

Extracellular structure surrounding plasma membrane

Plasma membrane:

Outer membrane of cells that controls cellular traffic (passage of materials). It has

property of permeability. There pores in it.

It is very sensitive to antigen exposure heavy metals, x-rays and fat solvents that lyse

(digest) the membrane.


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Transport in Cells:

All cells acquire the molecules and ions they need from their surrounding. There is an

unceasing traffic of molecules and ions. This action is carried out by tow ways which are:

1-Passive Transport

1-Diffusion: Molecules and ions move spontaneously down their concentration gradient

(i.e., from a region of higher to a region of lower concentration). The plasma membrane

is differentially permeable because some particles can pass through, others cannot.

a-Osmosis

Osmosis is the diffusion of water across a semipermeable membrane. Tonicity refers to

the relative concentration of solute on either side of a membrane.

Isotonic

In an isotonic solution, the concentration of solute is the same on both sides of the

membrane (inside the cell and outside.

Hypotonic

A hypotonic solution is one that has less solute (more water). Cells in hypotonic

solution tend to gain water.

Hypertonic solution

A hypertonic solution is one that has a high solute concentration. Cells in a

hypertonic solution will lose water.

b-Facilitated Diffusion

Facilitated diffusion involves the use of a protein to facilitate the movement of molecules

across the membrane. In some cases, molecules pass through channels within the protein.

In other cases, the protein changes shape, allowing molecules to pass through.

2-Active Transport: Molecules and ions can be moved against their concentration gradient in this type, the

energy of ATP is used to enforce ions or small molecules or even particles through the

membrane against their concentration gradient.

a-Direct Active Transport

The cytoplasm of animal cells contains a concentration of potassium ions (K+) as much as

20 times higher than that in the extracellular fluid. Conversely, the extracellular fluid

contains a concentration of sodium ions (Na+) as much as 10 times greater than that

within the cell. These concentration gradients are established by the active transport of

both ions. The same transporter, called the Na+/K

+ ATPase, does both jobs.

b- Indirect Active Transport

Indirect active transport uses the downhill flow of an ion (electrochemical differences)to

pump some other molecule or ion against its gradient. The driving ion is (H+) which is

pumped out the membrane to join glucose molecule. Later the ion is pumped back to

inside the cell by the ATPase.

c-Vacoules

The processes by which a cell engulfs or get red of material, these are:

-Endocytosis: a vacuole is formed that contains the material that has been engulfed.

-Exocytosis: moves material to the outside. A vesicle fuses with the plasma

membrane and discharges its contents outside. This allows cells to secrete

molecules.

-Pinocytosis: moves solutions to the inside by means of very small vesicle.


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Cell Division

The unique and fundamental property of protoplasm is its power to grow and multiply by

cell division. There are three types of cell division occur in living organisms, these are:

1.Amitosis of direct cell division.

2.Mitosis or indirect cell division.

3.Meiosis or reduction division.

1. Amitosis or direct cell division:

This is found in mainly in prokaryotes like cyanobateria, bacteria, yeast etc. some

protozoa's also divide by amitosis. The process is a means of reproduction. During it the

nucleus elongates and a constriction appears in the center resulting in a dumb bell shaped

structure. The constriction deepens and the nucleus gets divided into two bits. There is no

spindle formation of chromosomes. Cytoplasmic division follows the nucleus division

and the cell gets divided into two daughter cells. Thus the amitosis is only a quantitative

division.

2. Mitosis or indirect cell division:

Mitosis occurs in the somatic cell of multicellular organisms and its chief function is to

increasing in size and in individuals. It is defined as a complex process leading to

formation of two equal daughter cells from a single parental cell. The mitosis is divided

into two main stages or sometimes called cell cycle: cytokiensis and karyokinesis.

Cell cycle

Interphase:

Cell cycle

Interphase is the time between divisions (in all types of divisions) or at which cell is not

dividing. The nucleus is surrounded by membrane as well the chromatin and nucleolus

are present. The phase is divided into three periods known as cell cycle:

-G1 during which the protein and RNA synthesis are carried out.

- S during which the DNA are replicated towards division time.

- G 2 during which the volume of the nucleus increases.

Prophase:

It is the first stage of the nuclear division and it takes longest time in mitotic division.

During which the chromatin shortens, thickens and coils into chromosomes and become

visible. Nuclear membrane disintegrates. Centriole pairs move to opposite ends of the

cell. Spindle fibers begin to form.

Metaphase:

The phase lasts only for a short duration. It is guided by the spindle fibers, the

chromosome pairs line up along the center of the spindle structure at equatorial plate.


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Anaphase:

The thickening of the chromosomes is increased. The chromatids begin to depart from

the centrioles. Every chromatid (now becomes chromosome) removes to opposite poles

of the cell by the spindle fibers.

Telophase:

Chromosomes return to chromatin. Spindle disintegrates. Nuclear membrane takes shape

again. Centrioles replicate. Membrane continues to pinch inward by the process called

cytokinasis (in plant cells a new cell wall is laid). When the process is complete, each cell

will have the same genetic material that the original cell had before replication. Each of

the daughter cells is also identical to each other. Note that once telophase is complete, the

cell returns to interphase.

Significance of Mitosis:

1. Mitosis is extremely regular process maintaining the qualitative and quantitative

distribution of heredity materials to daughter cells. The process takes 3-10 hours in

plant cell and18-20 hours in animal cell,

2. It maintains the diploid number of chromosome of species.

3. The process results in growth and development of the organism. Adult human body

(75 kg in weight) consists of 60 trillion (60 000 000 000 000) cells derived from one

cell. The growth is very rapid in embryo so and it has three types in adult animals:

cell not dividing (arrested) as nervous cells, dividing in some cases as liver cell and

dividing continuously as skin cell.


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4. The process results in replacement of dead cells e.g. epidermis, RBC and gut (50 000

000 000 cells/ day).

5. The process plays an important in the asexual reproduction.

3. Meiosis or Reduction Division

Meiosis is a special type of division. All gametes have half the number of chromosomes

that regular cells have. Gametes are created through the process of meiosis. Meiosis

involves two divisions, which create four haploid cells.

The first meiosis division:

Interphase: it consists of same G1, S, and G2 phases

Prophase I: This phase takes longest time and it is complex .All chromatin material makes a copy of

itself, then pairing of homologous chromosomes takes place. Chromosomes grouped into

tetrads i.e. chromosome having two chromatids. Some crossing over may occur at

chiasma between opposite chromatids. The tetrads line up and pull apart by a process (

terminalization ). Once the chromosome pairs are at opposite poles of the cytoplasm.

Nucleolus disappears.

Metaphase I: The nuclear membrane disappears. The centrioles are jointed by spindle

fibers, which develop from tubules. The bivalents chromosomes arrange themselves on

the equatorial plate. The centromeres lie towards poles.

Anaphase I: each homologous chromosome of bivalent moves towards the opposite

poles. The centromere does not divide (it divides in mitosis).

Telophase I: the chromosomes reach the respect poles and become indistinct. Nucleolus

appears. Cell membrane is formed in animal cells by furrowing (cytokinasis). Finally

two cells formed. The two cells formed do not have the same genetic material; they have

the half number of chromosomes.

The second meiosis division:

The second meiotic division is a mitosis in which both the chromosomes and cell are

divide. The main difference is DNA does not duplicate as interphase of mitosis.

Prophase II: the centrioles divide into two and migrate to opposite poles. Nucleolus and

nuclear membrane disintegrate.

Metaphase II: It is of very short duration. Chromosomes line up at the center (equatorial

plate). The centromeres divide separating the two chromatids. The centromeres are

attached to chromosomal spindle fibers.

Anaphase II: the daughter chromosomes migrate to opposite poles. The movement is

due to the contraction of the chromosomal spindle fibers and continuos stretching of

spindle fibers.

Telophase II: the daughter chromosomes reach the opposite poles.. Nucleolus and

nuclear membrane reappear so daughter nucleus is formed. The cytoplasm then divides

(cytokinasis). The nucleus is haploid (half number of chromosomes). As the result four

cells are formed.

In male organisms the four new cells are all the same size. In females one of the four cells

receives the bulk of the cytoplasm material. This becomes the functioning egg while the

other three smaller cells disintegrate.


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HISTOLOGY

The structure of tissues

Histology is the study of animal and plant tissues. Tissues are defined as cells with their

ground substance acting together in the performance of a particular function. Tissues are

routinely cut into thin translucent sections that are then differentially stained and

examined under a microscope.

The primary tissue categories in animal histology are structurally there are four types of

tissue (1) epithelial tissue (2) connective tissue (3) muscular tissue (4) nervous tissue.

(1) Epithelial tissue

1-Epithelial tissues are composed of closely aggregated cells with very little

extracellular matrix.

2-The functions of epithelia are as a protective covering, absorption, secretion, sensation

and contractility. 3- Embryonically, the epithelia derive from all three embryonic tissues

4-Epithelial tissue is often associated with a basement membrane made of thin fibers and

ground substance.

5-Epithelial cells often have adaptations at their luminal surface to increase surface area

for absorption or to help move substances over the epithelial surface e.g. cilia

Structural types of epithelia:

(A) Simple, one layer and (B) Compound (stratified)

(A) Simple epithelia:

it Characterized by that cells be found as a single layer (simple). it is classified as follws:

(I) Squamous Epithelia:

These consist of greatly flattened cells cemented together to form a single layer which

under the microscope. They occur in the linings of abdominal cavities, the heart, blood

vessels, the walls of alveoli and in the outer layer of the elementary canal.

(II) Columnar Epithelia:

The cells of these are brick-shaped. The entire lining of the elementary canal (except

esophagus, buccal cavity and anus) and it’s associated with glands consisting of this type

of cells. Those of the villi of the small intestine have an outer striated border..

(III) Ciliated Columnar Epithelia:

In these the cells are columnar but possess cilia (cytoplasmic thread) on their outer

border. They are found in the linings of the trachea and larynx, the larger bronchiole

tubes in the lungs, nasal passage and fallopian tubules.


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(IV) Cubical (cubiodal) Epithelia:

The cells of these are cubical in shape. The nucleus is spherical in shape and is found in

the center of the cell. Cubical epithelium is found in the vessels of the thyroid gland,

walls of the duct of some glands as salivary gland, in the kidney and ovary (germinal

epithelium). Their function is mainly protection and execration.

(V) Pseudostratified Epithelia: the cells of this type of tissue begin at the basement

membrane and only few reach the surface. The nuclei appear at two levels giving the

tissue-stratified appearance. These are present in vas-difference, salivary gland, and nasal

septum.

(VI) Ciliated Pseudostratified Epithelia: the same as above but the in the surface there

are cilia as in trachea and bronchi. The function is trapping and moving pollutant.

(B) Compound (stratified) epithelia:

They are characterized by that have more than one layer of cells.

The tissues are divided into four types according to structure and arrangement of the

outer layer to the following:

(1) Squamous compound (stratified) Epithelium:

The inner layer is formed of cubical or short columnar cells; these cells are dividing

continuously forming new cells which have different shapes. These cells move towards

the outer layer, meanwhile they are compressed and become squamous in shape. They

also died because there is no blood supply so form horny layer. They occur in the skin

and the linings of esophagus of mammals.


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(II) Cubical compound (stratified) Epithelium:

The inner layer is formed of short columnar cells. The outer layer formed of cubical cells.

The cells in-between them have no definite shape. They occur in human sweet gland.

(III) Columnar compound (stratified) Epithelium:

The inner layer is formed of short columnar cells. The outer layer formed of columnar

cells. The cells in-between them have no definite shape. They occur in the many

excretory glands

(VI) Ciliated Columnar compound (stratified) Epithelium: The inner layer is formed of short columnar cells. The outer layer formed of ciliated

columnar cells. The cells in-between them have no definite shape. They occur in the

epithelia of the vas-difference.

(V) Transitional Epithelium: The layers are few formed from small cells when the organ fills and become of so many

layers when it relaxes. The intercellular matrix is mucous so the cells hang on each other

easily. They occur in elastic organ like urinary tube and bladder.


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2-Connective tissue

1-These tissues are responsible for cushioning, supporting and maintaining form within

the body.

2-The major constituent of connective tissue is the ground substance, which is composed

of protein fiber (gelatinous), fluid as in blood and solid matrix as in bones.

3-Most connective tissues are derived from the mesodermal layer.

4-There is no basement membrane.

There are three types of connective tissue as follows: -

1. Connective tissue proper:

2. Skeletal connective tissue

3. Vascular connective tissue

Types of connective tissue proper:

1-Areolar connective (loose connective tissue):

This type of the tissue has a reticular shape. Connective tissue is found in sheaths around

the blood vessels, and surrounding f muscle cells. It is well vascularized and contains

many types of cells and fibers.

Fibroblasts are the most common cells in connective tissue and are responsible for

making the fibers and the ground substance. They have a large ovoid nucleus, and well-

developed endoplasmic reticulum and Golgi apparatus.

Macrophages are resident phagocytic cells and have an oval shaped nucleus, well-

developed Golgi complex, many lysosomes and a prominent rough ER. They migrate into

the connective tissue.

Mast cells They secrete the ground substance. Secretary granules within mast cells

contain histamine, sertonin, and anticoagulant heparin. Mast cells are involved in allergic

reactions.

Plasma cells These large ovoid cells are responsible for making antibodies, they become

much more prevalent in areas subject to invasion such as the intestine or where there is a

chronic infection.

Others: there are many cells like eosinophill and lymphocytes.

Collagen (white) fiber it is stronger and less flexible and consisted of a protein called

collagen occurs in wavy bundles.


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Elastic (yellow) fiber it is more flexible consisted of a protein called elastin occurs in

singly though they branch and coalesce with one another forming a network.

2-Dense connective tissue (Fibrous or white): has many collagen fibers arranged in

bundles and has fewer cells. It is stronger and less flexible. It can be found in tendons and

ligaments.

3-Elastic (yellow) connective tissue: it has numerous bundles of elastic fibers with

interspersed flattened fibroblasts and collagen fibers. This tissue is very elastic. It is rare

but can be found in the ligaments of the vertebral column and blood veins.

4-Reticular tissue supplies the supporting framework for bone marrow and lymphoid

hematopoitic (blood cell making) organs. This type is found in bone marrow and the

spleen and liver.

5-Adipose stores lipids. In men it normally represents some 15-20% of body weight and

in women, 20-25% of body weight. It also helps to hold some organs in place.

In human infants and other mammals, a second type of adipose tissue is present called

brown adipose. It has numerous mitochondria and is specialized in heat generation.


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6-Mucous is a special type of connective tissue contains a few fibers and the matrix is

gelatinous. It is found in embryonic organs and the placenta.

B- Skeletal connective tissue:

1-Cartilage

Cartilage can be found in areas where shock absorbing or sliding are needed. The cells

(chondrocytes ) are embedded in the matrix, inside capsules (lacuna). There are three

types of cartilage based on variations in matrix composition: -

1-Hyaline cartilage, the most common form is hyaline cartilage. The matrix is clear and

there are no fibers inside (glass-like). It can be found on the articulating surfaces of

bones, walls of large respiratory passages, ventral portion of the ribs. Hyaline cartilage

forms the fetal skeleton that is later ossified and becomes bone.

Chondrocytes or cartilage cells are large and rounded each lying in a space - lacuna -

enclosed by matrix. Cells often are grouped in nests of 2, 4, or 6.

2-Elastic cartilage, the matrix contains many elastic fibers. It can be found in the auricle

of the ear, ear canal, eustachian tube, and epiglottis. It is flexible than the hyaline kind.

3. Fibrocartilage Fibrocartilage contains a dense network of collagen fibers amongst which are dispersed

only a few chondrocytes in lacunae. It is located between tendon and bone, bone and

bone, hyaline cartilage and in the intervertebral (IV) disc.


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2-Bone

Bone, on gross observation, has two forms.

Spongy bone (Cancellous) is found in the center of flat bones and the

ends of long bones.

Compact bone is a dense tissue seen in the shafts on long bones and

surrounding the spongy bone. Red (hematogenous) bone marrow is

found in the ends of long bones and center of the flat bones of the skull

and vertebra. The bone is composed of units called Havarsian system.

The are in-between the units is called non- Havarsian.

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C- Vascular connective tissue:

Blood might be classed as a specialized connective tissue because it is not connecting

tissues but has mesoderm origin. The matrix is plasma (90% water, 10% proteins,

inorganic salts, aminoacids, vitamins, hormones and others). it consists the following:

Red blood corpuscles/Erythrocytes (RBCs)

White blood cells/Leucocytes (WBCs)

Platelets

(A)Erythrocytes (Red Blood Cell = RBC's)

Biconcave discs; close to 7.5 µm in diameter. Comprise a flexible membrane enclosing

haemoglobin. Mature RBCs have no nucleus in mammals but it is nucleated in fishes,

reptiles, and birds. Erythrocytes also lack Golgi body, ER, ribosomes or mitochondria.

RBCs count in man is 5 millions /micoliter and 4.5/ micoliter million in women

Life span is estimated to be around 120 days, then the RBC is sequestered in the spleen,

liver or bone marrow to be phagocytosed by macrophages. The spleen takes the iron and

the other materials used by the liver in production of bile. RBC manufacture

(Haemopoiesis) takes 24-48 hours in maturation and is being in the liver and the spleen at

embryonic development then in bone marrow at maturation.


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(B)Leucocytes (White Blood Cells = WBC's)

These are nucleated cells, their count is 7000/ micoliter. They divided according to the

granularity of their cytoplasm into two groups - granular and agranular.

1. Granular leucocytes

All kinds appear round in a smear. They have granules in the cytoplasm. There are three

types of granular cells:

1. Neutrophil

Nucleus has three or more lobes or segments connected. They comprise 70 %of

leucocytes. They are 12-15 microns in diameter. The cytoplasm contains small granules

that are primary lysosomes containing numerous enzymes. These phagocytic cells

surround and engulf bacteria and constitute a defense against invasion.

2.Eosinophil (acidophill)

Eosinophils have a diameter of 12-15 microns and.

Nucleus is bilobed.

Cytoplasm has many large, eosinophil granules

They comprise 3 % of leucocytes.

An increase in the absolute number of eosinophils in circulation is associated with

allergic reaction and parasitic infection.

3.Basophil

(a) Nucleus is S-shaped sometimes twisted.

(b) basophilic cytoplasmic granules, containing heparin and the vasodilator,

histamine.

(c) They are rare; 1% of leucocytes.

2. Agranular leucocytes

1. Lymphocytes are of two forms:

Small spheroid cells about 18 µm in diameter and large, spheroid

nucleus , very little cytoplasm and about 12 µm diameter.

Lymphocytes circulate in blood and lymph systems and migrate to CT and

mucous membranes.

They amount to 22 per cent of the leucocytes.

They have a role in immunity and antibodies formation.

2.Monocyte( Macrophages)

Large, cells about 12-20 µm in diameter and have horse- shoe like nucleus.

Macrophages, by releasing cytokines after activation, coordinate inflammatory

and defensive reactions.

They comprise 3 % of the leucocytes.


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Blood Plasma

The matrix of the blood tissue is pale yellowish solution consists of 90% water and 10%

protein (fibrinogen, albumin and globulins). In addition there are calcium and potassium

bicarbonates and glucose, amino acids fatty acids and hormones.

Platelets (clotting and vessel-sealing)

1.Rounded or ovoid parts of cells, 2-5 µm diameter and counted to be 200,000 to 400,000

per microliter of blood in man.

2. These cell fragments originate from large cells in the bone marrow called

megakaryocytes, have a lifespan of about 10 days and are non-nucleated.

3. Platelets adhere to collagen, neutrophils and monocytes, and especially to each other;

this platelet aggregation is used to seal defects in blood-vessel walls. Platelets clot by

secreting thrombokinase or thromboplastin.

4. They also release from their granules several factors, e.g., serotonin and cytokines,

having vasoconstrictive and other actions.

Bone marrow

This reticular tissue has relation with blood. It has two forms red and yellow. The yellow

reserve lipids and fats. The red manufactures the blood cells.

Lymph (interstitial or tissue fluid)

Plasma = blood - blood cells

Lymph = plasma - proteins

The lymphatic system is formed of capillaries- lymph vessels -lymph nodes lymph ducts

to venous blood circulation.

(3)-Muscular tissues

These tissues form the body muscles. The unit forming these is special cell called muscle

fiber. The majority part of cell is a long cytoplasmic fiber (myofibril) which is a

contractile filament and the left of the cytoplasm is called sarcoplasma.

1/ Most muscular tissue is derived from mesoderm.

2/ The muscle fiber is itself a cell and muscle has relatively little extracellular tissue.

3/ The three kinds of muscle

(a) Skeletal/striated/voluntary

(b) Cardiac/heart/(striated)

(c) Smooth/unstriated/involuntary/visceral.

Smooth muscle cells are spindle shaped and have oval-shaped uni-nuclear (one nucleus).

The length of the cell ranges 20 microns in blood vessels to 200 microns in intestine. The


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fiber (muscle cell) may be found as solitary as the skin or reticular as in the respiratory

tract or dense as in the alimentary canal (longitudinal and circular muscles). They Locate

at walls of hollow organs, i.e. stomach, intestine, uterus and urethra Functions of these

tissues is the involuntary movement - i.e. churning of food, movement of urine from the

kidney to the bladder.

Skeletal muscle (striated)

Skeletal muscle cells run the full length of a muscle and cylindrical in shape with the

diameter of 0.01-0.1 or up to 0.4 millimeter. Note the striation characteristics of this

muscle type. These cells, are multinuclear locate at the periphery in mammals

(syncytium). Every fiber is consisted from two types of white and dark strips, which are

chemically, are proteins called myosin and actin respectively. The fiber is surrounded by

connective tissue called perimysium.

These muscles are associated with the skeleton and are functioning as voluntary

movement. Muscles are connected to bones by tendons. Bones are connected to other

bones at their joints by ligaments.

Cardiac muscle Cardiac muscle cells are cylindrical, branched and striated but less than

above. The nucleus is oval-shaped. There are intercalated discs. The tissue Locates only

at the heart Function: involuntary, rhythmic contraction

(4) Nervous tissues

Nervous tissue derives from the embryonic ectoderm under the influence of the

notochord. The ectoderm differentiates to form the neural tube from which all of the

central nervous system derives. The two types of the cells are neuroblasts (nerve cells)

and the spongyblast called glial cells assist neurons by support, protection, defense and

nutrition of the neurons. There are about 10 times more glial cells than neurons in the


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brain. Glial cells create the microenvironment needed for neuronal function and

sometimes they assist in neural processing and activity. Neurons are independent

functional units responsible for the reception, transmission and processing of stimuli.

Structure of the nerve cell:

In general, neurons consist of three parts; the cell body, where the nucleus and organelles

are located; dendrites, which are processes extending from the cell body that receive

stimuli from the environment or other neurons; and the axon, which is a long single

process extending from the cell body for the transmission of nerve impulses to other

cells. The axon usually branches at its distal end and each branch terminating on another

cell has a bulbous end. The interaction of the end bulb with the adjacent cell forms a

structure called a synapse. Synapses are specialized to receive a signal and convert it into

an electrical potential.

Types of the nerve cell:

Most neurons found in the human body are multipolar, meaning they have more than two

cell processes with only one being an axon and the remaining processes being dendrites.

Bipolar neurons of the retina or olfactory mucosa have one dendritic process and an axon

coming off the cell body. Unipolar neurons found in the spinal cord ganglia enable

sensory impulses picked up by the dendrites to travel directly to the axon without passing

through the cell body.

Functional types of the nerve cell: Neurons may also be classified according to function.

1- Sensory neurons are involved in the reception and transmission of sensory stimuli.

2-Motor neurons send impulses to control muscles and glands.

3-Interneurons, act as go- between neurons as part of functional networks.


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( عديدة االقطابخلية عصبية )(Poly polar)

cell and tissues rebat uni

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