Lesson 3

1. +
Levels of Organisation
The human body has five levels of organisation

2. +
Learning Objectives
To be able to:
 Explain how cells are specialized to
 Determination, Differentiation, Tissue, Organ, Organ system
Keywords:

3. +
Recap!!
 How many cells can you name? You have 15 seconds!

4. +
Started from the bottom now we’re
here…
 Multicellular organisms (like us!) are made up of cells, but
different cells have different functions.
 We are a collection of specialized cells that work together –
cells that developed from a single zygote
 Zygote divides and differentiates into more than 200 different
types of human cells.
 Cell specialization involves 2 main steps
- determination
- differenatiation

5. +
Determination
 The cells produced during the first few divisons = embryonic
stem cells
 Embryonic stem cells have the potential to become ANY type of
specialized cell in the body.
 After a number of weeks, most stem cells become committed to
develop into only one type of cell… DETERMINATION

6. +
Differentiation
 Differentiation is the process by which committed cells gain the
structure and functions of highly specialized cells.
 This is done by turning on or turning off specific genes in the
cell, allowing them to perform specific functions within the body
What are the functions of:
- muscle cells?
- sperm cells?

7. +
Differentiation
 Differentiation is the process by which committed cells gain the
structure and functions of highly specialized cells.
 This is done by turning on or turning off specific genes in the
cell, allowing them to perform specific functions within the body
Muscle cells – produce movement by contracting and relaxing
Sperm cells – develop whip like tails that enable them to swim

8. +
Uh oh…!
 However…. not all cells continue to develop into specialized
cells.
 Cell death – known as apoptosis – is also a normal part of
development
EG: the spaces between our fingers are due to the death of cells
that were there when our hands were first formed

9. +
 CELLS
 TISSUES
 ORGANS
 ORGAN SYSTEMS
 ORGANISM
The levels in the human body…

10. +
 CELLS
 TISSUES
 ORGANS
 ORGAN SYSTEMS
 ORGANISM
Each type of specialized
cell performs a specific
task
The levels in the human body…

11. +
 CELLS
 TISSUES
 ORGANS
 ORGAN SYSTEMS
 ORGANISM
Each type of specialized
cell performs a specific
task
Groups of similar cells working
together – 4 types (epithelial,
connective, muscle & nervous)
The levels in the human body…

12. +
 CELLS
 TISSUES
 ORGANS
 ORGAN SYSTEMS
 ORGANISM
Each type of specialized
cell performs a specific
task
Formed by different
types of tissue that
function together
Groups of similar cells working
together – 4 types (epithelial,
connective, muscle & nervous)
The levels in the human body…

13. +
The levels in the human body…
 CELLS
 TISSUES
 ORGANS
 ORGAN SYSTEMS
 ORGANISM
Each type of specialized
cell performs a specific
task
Formed by different
types of tissue that
function together
2 or more organs
working together
Groups of similar cells working
together – 4 types (epithelial,
connective, muscle & nervous)

14. +
The levels in the human body…
 CELLS
 TISSUES
 ORGANS
 ORGAN SYSTEMS
 ORGANISM
Each type of specialized
cell performs a specific
task
Formed by different
types of tissue that
function together
2 or more organs
working together
Groups of similar cells working
together – 4 types (epithelial,
connective, muscle & nervous)
Together, the organ systems
make up the entire organism

15. +
Example

16. +
Major Organ Systems
 How many can you name?
 What organs do they consist of?

17. +
 Circulatory
 Digestive
 Endocrine
 Excretory
 Immune
 Integumentary
 Muscular
 Nervous
 Reproductive
 Respiratory
 Skeletal

18. SYSTEM MAJOR TISSUES &
ORGANS
PRIMARY FUNCTION
Circulatory heart, blood, vessels, blood,
lymph nodes, lymphatic vessels
transports O2, nutrients, wastes; helps
regulate body temperature
Digestive mouth, pharynx, esophagus,
stomach, intestines, pancreas,
gallbladder, liver
breaks down & absorbs nutrients, salts
& water; eliminates some wastes
Endocrine hypothalamus, pituitary, thyroid,
parathyroid, adrenals, pancreas,
ovaries, testes
influences growth, development,
metabolism; helps maintain
homeostasis
Excretory skin, lungs, kidneys, bladder eliminates waste products; helps
maintain homeostasis
Immune white blood cells, thymus, spleen protects against disease; stores and
generates white blood cells
Integumentary skin, hair, nails, sweat & oil
glands
acts as a barrier against infection,
injury, UV radiation; helps regulate
body temperature
Muscular skeletal, smooth & cardiac
muscles
produces voluntary & involuntary
movements; helps circulate blood &
move food through digestive system
Nervous brain, spinal cord, peripheral
nerves
regulates body responses to change;
processes information
Reproductive male: testes, penis
female: ovaries, fallopian tubes,
uterus, vagina
produces reproductive cells; provides
environment for embryo in females
Respiratory nose, sinuses, pharynx, larynx,
trachea, lungs
brings in O2 for cells; expels CO2 &
water vapour