l1_cells structure and functions

Mdm Nor Syahida binti AliahmatBasic Biology

Foundation In Science

Cell Structure

and Functions

The Cell theoryTypes of cells: Prokaryotic or eukaryotic cellsCell componentsSpecialized cells

What you will learn ….

The Cell Theory

M. Schleiden T. Schwann R. Virchow

All organisms are made up of similar units of organization called cells

The Cell TheoryCell

theory

Living things are made up

of cells

The cell is the basic unit

structure and function

All cells come from pre-

existing cells by division

Cells contain hereditary

information – passed on to

new cells during cell

division

Types of cells

Prokaryotes

Cells with no nucleus or organelles within their membranes.

Eukaryotes

Cells that contain nuclei and organelles

surrounded by a membrane.

• Smaller than the eukaryotic cells.• Prokaryotic Before nucleus• Single-celled organism.• Lacks membrane-bound organelles.• DNA located in the cell (nuclear area/nucleoid) No

enclosed by a membrane.• Have cell wall, plasma membrane, flagella, ribosomes

Prokaryotic Cell

Prokaryotic Cell•O

btain energy from light & carbon from fixing CO2 (inorganic compound).

Photoautotrophs

•Obtain energy chemically & carbon from fixing CO2 (inorganic compound).

Chemoautotrophs

•Obtain energy from light & carbon from ingesting other organisms.

Photoheterotrophs

•Obtain energy & carbon from organic compounds by ingesting organisms.

Chemoheterotrophs

Cell wall:

•Unique cell walls surrounding their plasma membranes.•It contains peptidoglycan.•It support and maintain its cell shape.•It also prevent rupture of the cell.

Plasma membrane:

•Made up of phospholipids, fully permeable.•It controls the exchange of waste materials and nutrients.•It can also be used as a receptor of hormones, neurotansmitters and other chemicals.

Ribosome:

•Tiny organelles.•Found in large number in the cytoplasm.•Made up of equal amounts of RNA and proteins.•Made in the nucleus•Function: sites of protein synthesis.

Naked DNA:

Genetic material (Unit of inheritance )Lies freely in the cytoplasm concentrated in a region (nucleoid).

Flagella:

•Long fibers that project from the surface of the cell.•Important in locomotion.

Mesosome:Invaginating during cell

division.Organize the separation of two daughter cells and help in the formation of the cross wall between daughter cells.

• Eukaryotic True nucleus• Membrane-enclosed organelles.• Multiple biochemical process can occur

simultaneously and independently.• The DNA is located in the membrane-bound

organelle called nucleus. • Have a supporting framework or cytoskeleton.

Eukaryotic Cell

SIMILARITIES & DIFFERENCES Both cells are enclosed by plasma membrane and

have cytoplasm and ribosomes. Both have DNA as genetic material.

Feature Prokaryote Eukaryote

Organisms BacteriaProtists, fungi, plant &

animal

Cell size Diameter 0.5-10 µm Diameter 10-100 µm

Cell division

• By binary fission, no spindle formation

By mitosis or meosis with spindle formation

in both.

Cell wallsMurein is main strengthening

compound of cell walls

Cellulose is main strengthening

compound of plant walls; chitin in fungi

Feature Prokaryote Eukaryote

Organelles• No membrane-bound

organelles• Have a membrane-

bound organelles

Genetic material

• No nucleus or nucleoli.

•Lies freely in the cytoplasm

•DNA region is called nucleoid

• Contain in nucleus• True nucleus bounded

by double membrane• DNA is associated with

protein & RNA to form chromosomes

Flagella Simple consisting of only one microtubule

Arrangement of multiple microtubules

Respiration (Electron transport system)

Mesosomes Mitochondria

Photosynthesis

No chloroplasts Chloroplasts containing membrane

Plant Cell Vs Animal Cell

Plant cell Animal cell

Has cell wall - cellulose No cell wall

Has fixed, regular shape Irregular shape that is not fixed

Has chloroplast No chloroplast

Has large central vacuole Has small vacuoles

Has plasmodesmata No plasmodesmata

Centrioles present in lower plant species Centrioles always present

Lysosome rarely found Lysosome usually present

CELL COMPONENT

S

Complex barrier of lipoprotein layers that surrounds & separates the cell from its external environment.

It also surrounds the organelles such as the nucleus, mitochondria & chloroplast.

Selectively permeable where the cell membrane regulates what passes into & out of the cell.

Some substances, like H2O, move freely through the cell membrane by a process known as osmosis.

Cell Membrane

1. In 1972: Suggested by S. Jonathan Singer & Garth Nicolson

2. The components of a plasma membrane: integral proteins, peripheral protein, glycoproteins, phospholipids, glycolipids, cholesterol & lipoproteins.

3. Cell membranes are composed of a lipid bilayer with globular proteins embedded in the bilayer.

4. “ Mosaic” The proteins are embedded in the membrane like the mosaic tiles embedded in mortar.

5. “Fluid” The proteins are free to move. They can only move from side to side though, not through the membrane.

The fluid mosaic

model

7. Plasma membrane thickness: 7-8 nm.8. Each molecule of the lipid bilayer has a hydrophilic

(polar or “water-loving”) end and a hydrophobic (nonpolar or “water-hating”) end.

9. The hydrophobic fatty acids of phospholipids (the non-polar tails) of each layer face each other and form the centre region of the bilayer.

10. The polar head groups face outside, one to cytosol and the other to extracellular space.

11. The lipid bilayer of the plasma membrane exhibits selective permealibility. o Ions and large uncharged polar molecules, such as

glucose, cannot pass through. Small uncharged polar molecules, such as water and urea, and hydrophobic molecules, such as the gases O2 and CO2, can pass through.

12. On the external surface of the membrane (act as identity markers):o Carbohydrate + lipids = Glycolipids. o Carbohydrate + proteins= Glycoproteins.

13. Membrane protein consist of globular protein:a. Peripheral proteino Confine to the outer and inner surface of the

phospholipid bilayer.o Loosely bounded to the surface of the protein.b. Integral protein (transmembrane protein)o Penetrate the hydrophobic core of the lipid bilayer.

Hydrophilic when contact with aqueous environment.

14. The fluid mosaic model proposed that proteins are free to move in the lipid bilayer.

15. Cholesterol is another component of the lipid bilayer. It gives mechanical stability to the membrane structure by restricting the movement of the phospholipids.

16. Cholesterol also gives the membrane flexibility and permeability and reduce leakage of small polar molecules.

1. Forms a boundary. 2. Give shape, mechanical strength and protection.3. Regulate and control the flow of materials in and out of

the cell.4. Provide the receptor sites to detect the presence of

chemical messenger.5. Important in cell-cell recognation: Glycoproteins 6. Join cells together: Linking with membrane protein.7. Attachment to cytoskeleton.8. Attachment sites for the enzyme.9. Divide a cell into separate compartments.10.Act as intracellular transport system.

Function of the cell membrane

• Rigid non-living wall located outside the cell membrane of plant cells.

• Composed of middle lamella, primary wall, secondary wall and plasmodesmata.

• Function give support & protection.• In land plants, the cell wall is composed of cellulose &

hardening material such as lignin. • Suberin waxy compound involved in water proofing of

some tissues.• Pores in the cell wall allowing substances to come in

contact with the cell membrane.

Cell Wall

Primary cell wall• Found in young cells & cells that are not well differentiated

such as meristem, parenchyma & collenchyma.• Thin, about 1-3 μm thick.• Consists of 25-30% cellulose, 15-25% hemicellulose, 35%

pectin & 5-10% protein.• Formed during cell growth.• Composed of loosely arranged microfibrils of cellulose in

matrix, which allow the cell to grow & stretch.• The matrix is built up of pectin & hemicellulose. • Very porous & allows the free passage of small molecules.

Secondary cell wall

• The protoplast begins to secrete a secondary wall after the cell has stopped enlarging.

• Composed of tightly arranged fibers of cellulose, which are often hardened by lignin.

• Much thicker than primary walls.• Very strong; it gives plants their ‘woody’ characteristics.

Middle lamella• Located between adjacent plant cells.• Composed of a gel-like material pectin.• It helps cells adhere to each other.

Plasmodesmata• Extremely thin strands of cytoplasm.• Extend through the walls of adjacent cells so that the

protoplast is connected.• Allow the movement of ions & small molecules from cell to

cell.• Unite many cells of a tissues/plant into 1 functional whole.• Substances can then pass from cell to cell much faster.

Maintains & determines cell shape Provides support & mechanical strength Prevents the cell membrane from bursting in a

hypotonic medium Controls the rate, direction of cell growth &

regulates cell volume. Acts as a physical barrier to pathogens Acts as a carbohydrate storage As economical products such as paper, wood,

fiber, energy etc.

Functions of the cell wall

• Cytoplasm: Jellylike substance contained within the plasma membrane.o Made up of: Cytosol (cytoplasmic solution)

and Cell organelles.• Cytosol contain water (80%) and soluble proteins.

Other substance include glucose, amino acids, vitamins, minerals, oil droplets and food granules.

• It is the home of the cytoskeleton, a network of cytoplasmic filaments that are responsible for the movement of the cell and give the cell its shape.

• Helps the material move around the cell by moving and churning: Cytoplasmic streaming

Cytoplasm & Cytosol

Function

Holds together all of the cell’s organelles &

divide them.

Place for the cell metabolism &

chemical reactions.

Provide movement of the cell & gives

its shape

Plays a role in the osmosis process

Contains nutrients & helps in dissolving

waste products

Organelles

• The structure inside the cell that directs cell activities.

• Found in all eukaryotic cells except RBC & mature seive tube cells.

• Controls protein synthesis & stored genetic information.

• Spherical in shape, sometimes elongated structure that contains DNA.

• Divided into:o Nuclear envelopeo Nucleoplasmo Nucleoluso Chromosome

• It communicates with the cytoplasm via pores.

Nucleus

• Nucleus is surrounded by nuclear envelope: Demarkets the nucleus from cytoplasm.

• Has 2 membranes perforated by nuclear pore.• Space between the 2 membranes are called

perinuclear space.

Nuclear envelope

• Almost identical to the cytoplasm, inside the nucleus.

• Located within the nuclear membrane.• Jelly-like material, 80% water with crystalloids &

colloids dissolved in it.• The crystalloids are:

o Glucose, ribose, deoxyribose, amino acids, organic acids, nucleotides, mineral ions.

• The colloids are:o DNA, RNA, protein histone.

• Function to connect & support the other solid organelle structures in the nucleus. It also keeps them separated from each other.

Nucleoplasm

• Spherical structure within the nucleus, composed of DNA, RNA & protein.

• The site for ribosome production. Ribosome are involved in the protein-making process.

• Protein synthesized in the cytoplasm enter through the nuclear pores and become associated with the newly made rRNA in the nucleolus.

• Producing small & large subunits of ribosomes. Later the ribosomal subunits exit to the cytoplasm through nuclear pore.

Nucleolus

• The genetic code of the chromosomes is made from a chemical called deoxyribonucleic acid or DNA.

• Each chromosome is a single very long piece of DNA and the genes are coded along this length of DNA.

• The DNA is twisted and wound over and over again then looped and attached to a protein scaffold to form a chromosome.

Chromosomes

• Chromatin: The form that chromosome s take up when the cell is not dividing.o Euchromatin: contain

active DNAo Heterochromatin:

Contain inactive DNA

Chromosomes

Function of nucleus

Stores genes & chromosomes

Organizes the chromosomes for

cell division

Produces ribonucleic acid

(RNA)

Coils & uncoils the DNA

• Solid spherical granules with diameter of 20-25 nm.• Each ribosome: 2 ribosomal subunits. Each consist of about

70 protein molecules and several rRNA molecules.• Found in 2 places in the cell:

o Bound ribosomeo Free ribosome

• Ribosome is the protein factory of the cell.

Ribosomes

Rough ER: • Consists of flattened sacs: Cisternae• The cytoplasmic surface of its cisternae

appears rough because of the presence of the ribosomes.

• Site for protein synthesis to be export from the cell for intracellular use.

• Proteins are modified within the ER.• Phospholipid synthesis and assembly of

multichain proteins also occur here.Smooth ER:• Consists of network of membranous tubules • No ribosomes are present.• Necessary for steroid synthesis, metabolism

& detoxification of substances in the liver, phospholipid synthesis & excitation-contraction coupling in skeletal muscles.

Endoplasmic reticulum

• Stack of flatten membranous sacs (cisternae).

• Finishes the post-transitional modifications, concentrates & package proteins for export or storage.

• It is also directs the destination of the protein package.

• The proteins made within the rough ER bud off in vesicles and are transported to the Golgi where the vesicles fuse with the membrane.

• The components are further modified, concentrated and packaged by the time they bud off as vesicles on the opposite side of the Golgi.

Golgi complex

• Means “Thread granule”• Rod-shaped structures that vary in

size & shape (2-8 μm in length).• It serves as the site for the

production of cellular energy (ATP) using Krebs cycle.

• Surrounded by 2 membranes. The outer forms the exterior of the organelle while the inner is arranged in a series of folds called cristae.

• The space between the inner & outer membranes is called intermembrane space while the compartment enclosed by the inner membrane is called the matrix.

Mitochondria

• Spherical membrane bound vesicles containing hydrolytic enzymes that can digest most biological macrmolecules.

• The size ranges from 0.05 to 0.5 micron in length.• Involved in intracellular digestion that are more numerous

in cells performing phagocytosis.• The most common lysosomal enzymes:

o acid phosphatase, ribonuclease, deoxyribonuclease, proteases, sulfatases & lipases.

• These enzymes function optimally at pH 5 and are most inactive at the pH 7.2.

Lysosome

• Lysosomal enzymes, synthesized on the rough ER are transferred to the Golgi for modification and packaging.

• Lysosomes also participate in the turnover of old, worn-out cellular organelles in a process called autophagy.

• It can also carry out autolysis where the whole cell is digested.• Lysosomal enzymes are also involved in the process of

inflammation.

Lysosome

Function of lysosomes

Carry out intracellular digestion

(phagocytosis)

Recycle the cell’s own organic materials

(autophagy)

Carry out programmed cell

destruction

Chloroplast & Plastids• Plastid are group of large organelles found in the

cytoplasm of plant cell but not in animal cells.o Chloroplast: Green colored plastids containing

chlorophyllo Chromoplast: Colored plastids rich in pigment

(carotenoids) – Give colors to the fruit, flower etc.o Leucoplast: Non-colored plastid containing no

pigments.

Chloroplast & PlastidsChloroplast: • Shape of biconvex disc • Consist of an envelope of 2 membranes separated by

narrow intermembrane space.• Stroma: Gel-like matrix• Lamellae: Well-developed system of internal chloroplast

membranes. • Intergranal lamellae: Connect one granum to another.• Thylakoid: Coin-like flatten sac.• Granum: Thylakoid that pile up forming stack.

• Fluid-filled sac bounded by single membrane called tonoplast.

• Fluid within the vacuole: cell sap.• Most commonly found in plant cells, vacuoles are

storage sites within a cell.• Site of pigment deposition: Anthocyanins• Plant defence: Tannin• Improving the surface area to volume ratio.• Helps to absorb the water.

Vacuole

• Types:o Food vacuole: formed initially by the engulfing or

phagocytosis of food particles.o Contractile vacuole: helps to pump excess water out

of the cells in many freshwater algae.o Central vacuole: most plant cells have a central

vacuole surrounded by a membrane called the tonoplast, which is part of the endomembrane system.

Vacuole

• Complex network of fine fibrils.• Function: cell shape, cellular movement.• Made up of:

o Microtubuleso Microfilamento Intermediate filament

Cytoskeleton

• Fine unbranched tubules with an outer diameter of 24 nm, a dense 5 nm thick wall and a central hollow core.

• The microtubules comprise of a helical arrangement of the protein “Tubulin”.

• Function:o Provide the necessary

intracellular transport system for the movement of organelles and vesicles.

o Form the internal skeleton of the cell and give it its shape.

o Form the main component in cilia and flagella.

o Draw the chromosomes to opposite polar of the spindle during cell division.

Microtubules

• Smaller, solid structures of about 6 nm in diameter.• Made of the protein actin and myosin contraction in

muscles.• Arranged helically.• Contracts when these proteins slide one over another.• Form a thin sheath under the cell membrane.• Involved in cellular functions of endocytosis, exocytosis and

cell movement.• Help in the movement of vesicles, granules and cytoplasmic

organelles.

Microfilaments

• Average diameter = 10 nm.• Bigger than microfilaments but smaller than the

microtubules.• Found only in animal cells.• Made of several proteins depending on the cell or

tissue type.• Eg. Keratins found in most epithelial cells. • Function: protect the skin, hair and nails from

abrasion and dehydration.

Intermediate filaments

SPECIALIZED CELLS

Plant TissueAnimal Tissue

Plant tissue

Meristematic tissue

Apical meristems

Lateral meristems (cambium)

Intercalary meristems

Permanent tissue

Dermal tissue

Ground tissue

Vascular tissue

• Grow and divide to produce new cells, never mature themselves.

• Meristematic cells Mitosis Various type of cell.• Structure of the cell:

o Small, thin-walled, with no central vacuole and no specialized features.

o Dense cytoplasm and nucleus occupies large part of the cell.

• Location: Divide to generate new cells near the growing point at the shoot and root tips.

Meristematic tissue

• Three types of meristems:a. Apical meristemso Occur at the tips of the root and the shootso Responsible for primary growtho Three parts: Protoderm, Procambium, Ground

meristemb. Lateral meristems (cambium)o Located at outer edge of stems and roots.o Take part in secondary growth.o 2 types: Vascular cambium and Cork cambiumc. Intercalary meristemso Present only in monocotyledon plants

Meristematic tissue

• Form by differentiation of meristematic cells Which become spcialised to perform specific function.

• Example: Protection, support, storage and transport of food and water.

Permanent tissue

Permanent tissue

Dermal tissue

Ground tissueVascular tissue

• Consists of epidermis and periderm

Epidermis• Single layer of closely packed cells• To cover and protect the plant• Secretes cuticle (coating that helps plants to retain

water)Periderm (Bark)• Replace epidermis in plants that undergo

secondary growth• Consists of cork cells. Cork tissue composed of

dead cells.

Dermal tissue

• Structure: o Large, thin-walled and usually have a large

central vacuole.o Least specialized of all plant cell types.o Shape is isodiametric with thin cell walls.o Living cells

• Location: Found in all the organs of a plant.• Function: Food storage and photosynthesis.

Ground tissue: Parenchyma

• Structure: Thick walls especially at the corners.• Location:

o Most often found in areas that are growing rapidly and need to be strengthened. Eg: stalk of leaves.

o Occurs as bundles of cells just beneath the epidermis.

• Function: Provide mechanical support for the plant.

Ground tissue: Collenchyma

• Structure: o Thick cell walls and built up in

a uniform layer around the entire margin of the cell.

o Consists of lignin that make the cell walls tough and hard.

• Location: Found in stems and also in leaf.

• Function: o Usually found associated with

other cell types, giving them mechanical support.

o Makes up the hard outer covering of seeds and nuts.

Ground tissue: Sclerenchyma

• Structure: Thick-walled tubes that can extend vertically through several feet of xylem tissue.

• Walls are thickened with secodary deposits of cellulose straightened by lignin

• Contain tracheids hollow, thin, long non-living cell, perforated so that water can flow from one tracheid to the next.

• Function: Passively conducts water and dissolved minerals from the roots to all the other parts of the plant.

• Contains sclerenchyma cells to add support.

Vascular tissue: Xylem

• Main components:o Sieve elementso Companion cells

Vascular tissue: Phloem

• End walls are perforated, this allows cytoplasmic connection.

• Sieve tube conducts the products of photosynthesis (sugar and amino acids) from the source (leaves) to the places where they are consumed/stored (roots, flowers, fruits)

• No nucleus and lack of organelles. They depend on the companion cells for many function.

Sieve Elements

• Located beside the sieve tubes.• Built up by compact protoplasma

and mitochondria.• Move sugars and amino acids into

and out of the sieve elements.• Provide energy (ATP) which is

needed to move sugars and amino acids from the cells into the sieve tubes by active transport.

Companion Cells

ANIMAL TISSUES

Epithelial cell

Cartilage

Bone

Nerve cells

Muscle cell

Blood cell

• Structure: Composed of closely aggregated cells arranged in flat sheets.

• Location: Tissue consisting of one or more layers of cells found on the external surfaces covering the body as well as the internal surfaces that line cavities, tubular organs and blood vessels of organs.

• Generally, the epithelial cells divided into 3 types depending on the shape of the cells. (squamous, cuboids & columnar)

• Distribution of the cells relates to the function of the cells.

• Function: protective covering, as well as in absorption, secretion, sensation and contractility.

Epithelial Cell

• Maybe present as a single layer (simple) or as multiple layers (stratified epithelia).

• Single layer: found in barriers that prevent diffusion such as in the lining of the alveoli of the lungs.

• Stratified epithelia: found in areas where protection is more important such as in the skin or the inside layer of the mouth.

• Epithelial tissue can be divided into 3 types:o Simple epithelium: One cell thick.

• (Squamous, Cuboidal, Columnar)o Stratified epithelium (Compound epithelium):

Two or more cells thick.• (Stratified squamous epithelium, stratified

cuboidal epithelium, stratified columnar epithelium, transitional epithelium)

o Pseudostratified epithelium: single layer of cells of different sizes, giving appearance of multilayerd.

• Structure: Consists of thin, smooth and strong sheets of cells.

• Location: Occurs in the endothelium of blood vessels and the outer layer of the Bowman’s Capsule.

• Function: o facilitate diffusion across it very thin structure.o Smoothens the passage of fluid and lubricates

movements.

Squamous epithelia

• Lines the villi of the small intestine as well as the outer borders of microvillis.

Cuboidal epithelia

• Location: Can be found in the collecting ducts and tubules of nephrons, salivary glands and sweat glands.

• Function: secretory and absorptive function. Eg: columnar epithelium of the intestine.

• Contains mucus-secreting goblet cells.

• Ciliated epithelia line the oviducts and respitory surfaces where the cilia cause movements of liquid such as the mucus stream to help clear away dust and bacteria from the lungs.

Columnar epithelium

• Made of several layers of cells which form a tough impervious barrier.

• The outermost layer of cells known as the generative layer is in an active state of mitotic cell division.

• This structure provides protection from abrasion.• Stratified squamos epithelium can be found in the

epidermis of skin and in the lining of the innermost layer of the esophagus.

• Stratified cubodial epithelium can be found in excretory ducts of sweat glands.

• Stratified columnar epithelium can be found in the secretory ducts of the mammary glands.

• Transitional epithelium can be found only in the urinary passage.

Stratified epithelia

• Appears to be layered but true layers do not exist because each cell touches a basement membrane that joins the epithelium to the underlying connective tissues.

• Found in the innermost layer of the trachea, bronchi and bronchioles.

Pseudostratified epithelia

• Specialized tissue which is hard and flexible to withstand mechanical stress without permanent distortion.

• Can be found in joints such as sliding joints and hinge joints. It acts as a shock absorber, cushioning bones during movement.

• Produced by chondrocytes that secrete protein matrix with no calcium carbonate.

• Nourished by of nutrients diffused from capillaries in the adjacent perichondrial connective tissue or synovial fluid.

Cartilage

• Acts as levers converting muscle contraction into movement.

• Hydroxyapatite:o the substance that gives bone its hardnesso made from calcium and phosphateo associated with collagen in bone, giving it its

strength and resistance.• 2 forms:

o Spongy boneo Compact bone

Bone

• Spongy boneo Found in the center of flat bones and the ends of

long bones.• Compact bone

o A dense tissue seen in the shafts of long boneso Surrounds the spongy bone of flat or short bones.o Formed by osteocytes located in the lacunae which

are arranged in concentric circles around the Haversian canals which contain blood vessels and nerves.

• Osteocyteso Secrete the matrix of calcium phosphate and

carbonate together with proteins.o Communicate with one another and receive

nutrition through the canaliculi, the thin channels penetrating the matrix.

• Nervous tissue found in:o Braino Spinal cordo Nerve

Neurons• Specialized for the conduction of nerve impulses. • Amitotic: If neuron is destroyed it cannot be replaced-No

mitosis• 3 common features:

o Cell body – contains the nucleus.o Dendrites – short fibers, impulses are brought in

towards the cell body.o Axon – single long fiber, takes impulses away from

the cell.o Axons meet at 3 junctions: other neurons (synapses) ,

muscles (neuromuscular junction), glands.

Nerve cells

• 3 types of neurons: sensory neurons, motor neurons, interneuron.

Sensory (afferent) neurons• Carries impulses from the sensory receptors to

the CNSMotor (efferent) neurons• Carries impulses from CNS to the effectors

(muscle and glands)Interneuron (associated) neurons• Connects one neuron with another.• Eg. Riflex arcs, interneurons connect the sensory

neurons with the motor neurons.

Neuroglia & Glial cells

• Cell that do not transmit impulses but support the activity of the neurons.

• 2 types of neuroglia: Schwann cells (CNS), oligodendrocytes (Peripheral NS)

• Produce myelin sheath surround the axons of the neuron.o Axon with myelin: Myelinatedo Axon without myelin: Unmyelinated

• Function of myelino Protection and insulation of the nerve fibreo Increase the rate of transmission of nerve impulses.

• Gaps between the myelin sheath

• 3 types of muscles:o Smooth muscleso Striated muscle

(skeletal muscle)o Cardiac muscle

Muscle cell

Smooth muscles• Called involuntary muscles – muscles that cannot be

controlled voluntarily.• Their cells are of variable lengths but are in the order

of 0.1 mm.• Can be found in the digestive tract and in the walls of

the trachea, uterus, artery and bladder.• The contraction is controlled by the brain through the

autonomic nervous system.• It contracts rhythmically, producing wave of

contraction such as in the peristalsis process.

Striated muscles• Also known as skeletal muscles because of their

anatomical location.• Formed from a large number of muscle fibers that

range in length from 1 to 40 mm and diameter from 0.01 to 0.1 mm.

• Each fiber forms a (muscle) cell and is distinguished by the presence of alternating dark and light bands.

• Attached to the bones via tendons.• Voluntary and form an essential part of the organ of

support and motion.

Cardiac muscles• Only found in the heart.• Also striated.• Differs from skeletal muscle:

o Involuntary muscleo When agitated, it generates a much longer

electrical impulse and the mechanical contraction also lasts longer.

o Does not require impulse from the brain – independent nervous control.

o Myogenic, it has its own pacemaker to generate excitation before it contracts.

• Consists of fluid and cells that flow in one direction in a closed circulatory system.

• The bone marrow is the source of all the cells of the blood.

• These includes:o Red blood cells (RBCs or erythrocytes)o White blood cells (WBCs or leukocytes) – 5 types.o Platelets (thrombocytes)

Blood cell

• Formed in the bone marrow.• Do not have a nucleus and are filled with the oxygen-

carrying protein, hemoglobin.• Biconcave shape and very thin membrane provide a

large surface for oxygen delivery.• Specialized cells for carrying oxygen.• An average RBC survives in circulation for 120 days.

Erythrocytes

• Found in circulation but may leave the circulatory system and migrate to the tissues to perform various functions.

• Form the defensive mechanism of the body at cellular level.

• Classified as granulocytes and agranulocytes, depending on the presence/absence of visible granules within the cellular cytoplasm.

Leukocytes

Leukocytes

Agranulocytes

Lymphocytes Monocytes

Granulocytes

Neutrophils Eosinophils Basophils

Granulocytes• Have granules in their cytoplasm.• Formed in the bone marrow.• 3 types:

o Neutrophils – have a nonsegmented horseshoe-shaped nucleus.

o Eosinophils- presence of many large and elongated granules that are stained red by eosin.

o Basophils- contain numerous granules that contain heparin and histamine. These granules stain blue with the typical hematoxylin/eosin stain.

Agranulocytes• Do not have granules in their cytoplasm.• Formed in the bone marrow and mature in the thymus

gland.• Divided into:

o Lymphocytes• spherical cells and nuclei.• very little cytoplasm.• lymphocyte–T cells – mature in the thymus gland,

participate in cellular immunity.• lymphocytes-B cells – mature in the bone marrow,

produce antibodies.o Monocytes

• oval, horseshoe or kidney shaped nuclei.• more cytoplasm than lymphocytes.• differentiate into macrophages in the connective

tissues.

• Also known as platelets.• Originate from large cells in the bone marrow called

megakaryocytes.• Have a lifespan of about 10 days and are non-

nucleated.• Metabolically active cell.• Promote blood clotting and repair gaps in the walls

of blood vessels.• Mature cell is small and has no nucleus.

Thrombocytes

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