Internal Environment of Multicellular Organism

1. The internal environment of a multicellular cell is referring to the medium surrounding the cell.
2. It consists of blood plasma and interstitial fluid. (also called the extracellular fluid)

Homeostasis

Homeostasis is the property of a system, especially a living organism, that regulates its internal environment so as to maintain a stable, constant condition.

Factors Affecting the Internal Environment.

1. Body temperature
2. pH value of the blood
3. Sugar level of the blood
4. Blood pressure
5. Osmotic pressure of the blood
6. Concentration of the oxygen and carbon dioxide in the blood

Importance of Homeostasis

Maintaining a suitable environment for all the enzyme function efficienly, and hence enable all biochemical reactions been carried out at their maximum rate.

Regulation of body temperature

Nervous system	Detect changes in body temperature
Integumentary system	Produces sweat when the surrounding is hot.
Circulatory system	Transports and distributes heat evenly through out the body
Muscular system	Shivering to produce heat when the surrounding is cool.

1. Different organ work together form an organ system.
2. The human body has eleven different organ system, namely the
1. Circulatory System
2. Digestive System
3. Reproductive System
4. Endocrine System
5. Nervous System
6. Respiratory System
7. Muscular System
8. Skeletal System
9. Excretory System
10. Lymphatic System (Immune System)
11. Integumentary System

Circulatory System

Organ: Heart, Blood Vessel
Function: Transport nutrients, gases and wastes to and from cells, helps fight diseases and helps stabilize body temperature and pH to maintain homeostasis.

Digestive System 

Organ: Mouth, Oesophagus, Stomach, Duodenum, Small Intestine, Large Intestine
Function: Breaks down food in the body, into a form that can be absorbed.

Reproductive System

Organ: Males: Testes, penis; Females: Ovaries, uterus, vagina
Function: Reproduce offspring.

Endocrine System

Organ: Pituitary, Thyroid, Adrenal gland, Pancreas, Ovary (female only), testis (male only)
Function: Secrets hormone. Hormones are chemical that play a role in regulating metabolism, growth, development and puberty, and also plays a part in determining mood.

Nervous System

Organ: Brain, Spinal Cord, Peripheral Nerves, Sense Organs
Function: Conduct impulses the the body, spinal cord and brain.

Respiratory System

Organ: Nose, Trachea, Lungs
Function: Allow gas exchange.

Muscular System

Organ: Muscle
Function:

• Initiates heart beat.
• Working with the skeletal system in movement and locomotion.

Skeletal System

Organ: Bones, Tendons, Ligaments, Cartilage
Function: 

• Supports the body.
• Protects the internal organ.
• Make red and white blood cells.
• Plays important role in movement.

Excretory System

Organ: Kidneys, Skin, Lung
Function: Eliminates the waste products of metabolism.

Lymphatic System (Immune System)

Organ: Lymphatic Nodes, Lymphatic Vessels, Spleen, Thymus Galnd
Function: 

• Remove the interstitial fluid from tissues.
• Absorbs and transports fatty acids and fats to the circulatory system.
• Produces immune cells.

Integumentary System

Organ: Skin
Function: Protects the body from damage,

Cell specialisation

1. Cell specialisation means division of labour among cells. Each type of cell specialises in a specific function.
2. Importance of Cell Specialisation
1. Cells can perform specific task with greater efficiency.
2. Enable multicellular organisms adapt to various environment.

Cell Specialisation in Animal

Cell	Function
Red blood cells	Transport oxygen
White blood cells	Destroy microorganisms. Engulf foreign substance in the blood stream.
Smooth muscle cells	Contract and release to produce movement
Nerve cells	Transmits nerve impulse

Cell Specialisation in Plant

Cell	Function
Palisade Mesophyll Cells	Carries out photosynthesis
Guard Cells	Control the size of the stomata pore to allow gaseous exchange.
Xilem	Transport water and mineral salt
Phloem	Transport disolved food.

Cell Organisation in Multicellular Organism

Cytology (Cell Biology)

Cytology is an academic discipline that studies cells. It's also known as Cell Biology.

Histology

histology is the study of the microscopic anatomy of cells and tissues of plants and animals.

1. Multicellular organisms are organisms that consist of multiple cells (more than one cell).
2. Multicellular organisms are more complex than unicellular organisms and hence  need many different types of cell to carry out their life processes.
3. This can be achieved through cell specialisation and cell organisation.
4. Examples of multicellular organisms are hydra, spirogyra, weeds, flowering plants, vertebrate and invertebrate animals.

(Hydra)

(Spyrogyra)