2.2

2.2 Cell Organisation

Multicellular organisms

Cell specialization

A zygote

A ball of cells (embryo)

Eight

Two cells Four cells

A ball of cells (embryo)

• Consist of one or more layer of cells.• Epithelium cells are tightly

interconnected, form continuous layer over body surfaces and inner cavity linings (digestive tracts and lungs)

• Some have glands (exocrine and endocrine)

• Skin epithelium forms a barrier against infections, mechanical injury and dehydration

• Intestine epithelium has goblet cells which secrete mucus into the digestive tract

• Trachea epithelium has small, hair like ‐projections called cilia

Epithelial tissue

(Lining and protection)

Cell organization in animals

Epithelial tissue

• Composed of muscle fibres • 3 types of muscle tissue: – Smooth muscle (intestine, blood

vessels, urinary and reproductive tract) • Involuntary movements • Contract slowly, for a long time

– Skeletal muscle (arms and legs) – On Demand • Voluntary movements • Contract, relax to move bones

– Cardiac muscle (heart walls) – Work, Work, Work, 24/7, 365 days a year • Blood pumping to body parts, involuntary

Muscle tissue

(Movement)

Muscle tissue

• Consists of various cells and fibres separated by extracellular matrix • Types of connective tissue:

– Loose connective tissue • Most widespread • Binds epithelia to underlying tissues and holds organs

– Dense fibrous connective tissue • A lot of closely packed collagenous fibres‐• Found in tendons (muscle bone connection) and ligaments ‐

(bone bone connection/joints)‐– Cartilage

• Strong and flexible • Support to nose, ears and covers bone ends at joints • Cartilage discs between vertebrae absorb pressure

– Bone • Cells embedded in collagen matrix, hardened by calcium • Harder than cartilage, protects organs, supports body

– Blood cells • Produced in bone marrow (ends of long bones) • Regulating, transporting and protective functions

– Adipose tissue • Tightly packed cells, storing fat • Found in skin dermis and around major organs • Energy reserve, insulation and protection • Each cell has an oil droplet, energy used up, the droplet

shrinks

Connective tissue

(Multiple Uses)

• Composed of neurones or nerve cells • Neurone has a cell body and nerve

fibres (dendrites and axons) • Neurons detect stimuli and transmit

electrical signals (impulses) to muscles/glands

• Directs and coordinates body activities

Nerve tissue

(Transfer information)

Loose and dense connective tissue

Bone tissue

Cartilage

Red blood cells

Adipose tissue

Cartilage

Bone tissue

Blood cells

Adipose tissue

Organs • Tissues work together to perform a specific function. These are

called organs. Examples are lungs, heart, kidneys, brain etc. Example: The skin:

• Consists of various tissues joined together • 2 main layers, the epidermis and the dermis • Epidermis is made of epithelial tissue, which constantly divides • Dermis is made of connective, nerve, epithelial and muscle tissue • Blood is supplied through blood capillary network • Nerve endings are scattered throughout the skin, transmit

impulses to nervous system • Epithelial cells produce hair follicles, sweat glands and oil glands

Organs

Skeletal system

Muscular system

Circulatory system

Lymphatic system

• Two main types of tissue in plants: – Meristematic tissue • Consists of small cells

with thin walls, large nuclei, dense cytoplasm and no vacuoles • Young, actively

dividing cells, undifferentiated, located at root tips and shoot buds

– Permanent tissue • Differentiated/partly differentiated mature tissues • Three types of permanent tissue:

1. Epidermal tissue » Outermost layer, covering stems, leaves and roots of

young plants » Flat, with large vacuoles » Walls that are exposed to air covered with waxy

waterproof cuticle » Cuticle reduces water loss, mechanical injury and

infection » Root cells have root hairs to increase water

absorption » Guard cells, containing chloroplasts, open and close

stomata

Guard cells and stomata

Waxy, waterproof cuticle

3. Vascular tissue –Continuous throughout the plant –Consists of: • Xylem –Consists of xylem vessels joined end to end

from root to leaf –No cytoplasm, easy water, mineral transport –Cell walls with Thickening Lignin™ for support

‘n strength • Phloem –Sieve tubes end to end, forming tube like ‐

structures –Transports organic compounds (carbohydrates,

amino acids)

• Organs in plants are leaf, stem, root and flower. Systems are root and shoot systems.

• Root system – all plant roots. Shoot system – stem, leaf, bud, flower and fruit. Stem, branch for support system. Leaf for photosynthesis. Flowers for pollination

Shoot system

Root system

INTERNAL ENVIRONMENT

• Internal environment consists of blood plasma, interstitial fluid (ISF) and lymph.

• Interstitial fluid (ISF) fills spaces between cells and bathes the cells. It exchanges substances with the blood plasma and the lymph.

• Physical factors and chemical factors of internal environment must be maintained.– Physical factors include temperature, blood pressure

and osmotic pressure .– Chemical factors include pH, salt and sugar content.

• Homeostasis is maintenance of constant internal environment for optimal cell performance. Any changes in the internal environment will cause homeostasis to kick in and work to cancel the change.

• This is governed by the negative feedback mechanism.

• Body temp. is regulated by integumentary system (skin+glands), nervous, circulatory, muscular and endocrine system. – Skin receptors detect rises in body temp, nerve cells

transmit the info to the hypothalamus, the brain’s temp control. It activates blood vessels’ dilation to allow more blood flow to skin for heat loss and sweat glands to produce sweat to increase heat loss.

• Oxygen and carbon dioxide levels are regulated by the respiratory, circulatory and nervous system.

• Circulatory system transports oxygen to cells and carbon dioxide to lungs. Level changes are detected by nervous system like an increase in CO2 and decrease in oxygen. Heartbeat and breathing increase to get normal oxygen and CO2 levels.

•

• Blood osmotic pressure is regulated by nervous, endocrine, excretory and circulatory systems.

• Chemical contents are regulated by excretory, circulatory, nervous and endocrine systems. Urea is transported to the kidneys by bloodstream to be excreted.

• pH is regulated by respiratory, circulatory and excretory systems by controlling H+(hydrogen ion), OH– (hydroxyl ion) and HCO3– (hydrogen carbonate ion) levels in blood plasma and interstitial fluid

Test yourself!

1. What is the function of contractile vacuoles in Amoeba sp.?

2. Draw and label the process of phagocytosis in Amoeba sp. Explain the process.

3. There are two main types of tissues in plants which are meristematic and permanent tissue. State the differences among the three types of permanent tissue.

4. Name the systems that are involved in regulating the blood sugar level.

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