UNIT 1: THE ORGANISATION OF THE HUMAN BODY.Introduction.Biology is the science to study the living things.
To define living things we need to use the special characteristics they have. These
characteristics need:
- To be exclusive of the living things
- To be common of all the living things
The characteristic to define living things are:
1. Their vital functions:
- Nutrition: capacity of living things to take matter and energy from the environment
and use it.
- Relation: capacity of living things to detect stimuli in the environment and to react.
One stimulus is a change in the environment like a sound, light, a taste, a smell,
some pressure, etc. And the response could be a movement, a secretion, etc
- Reproduction: capacity of living things to make copies of themselves.
2. All the living things are made up of the same molecules: biomolecules.
3. They are made up of cells. Some living things are only one cell: single cell
organism, and other are many cells, they are multicellular organisms.
To define a cell we use the cell theory. This theory says that the cell is the basic
structural, functional and genetic unit of an organism. This means:
. All the living things are made of cells.
. A cell is the smallest part in a living thing that carries out its vital functions.
. A cell comes from successive divisions of one initial cell, the egg cell or zygote.
Characteristic of cells.Shape: it is variable, it could be spherical, prismatic, star-shaped, etc.
Size: it is variable too, but in general it is small because we need to use a microscope to see
a cell and because the unit to measure a cell it is the micron.
Structure:
All the cells have the following structures:
- A cell membrane: a fine layer that separates the cell from the outside environment
and allows substances to go in and out.
- The cytoplasm: substance inside the cell. It can contain many types of organelles (it
depends on the type of cell) and it is where the majority of the vital chemical
functions take place.
- The genetic material (DNA) with the necessary information to direct and control the
cell’s functions.
Types of cells according to their structure:
1. Prokaryotic cells: they are the simplest cells, the first ones that appear in the world
and their genetic material is free in the cytoplasm. Bacteria are examples of them.
2. Eukaryotic cells: they have the most complex cells, they have the genetic material
surrounded by a membrane that made the nucleus. There are two types of eukaryotic
cells: animal cells and plant cells, Both are cell membrane, cytoplasm and nucleus.
And inside the cytoplasm there are cytoskeleton, endoplasmic reticulum, golgi
apparatus, ribosome’s, lysosomes, mitochondria. Centrioles is a structure of the
animal cells, and chloroplast, cell wall and vacuoles are typical of the plant cells.
Structure and function of the organelles.Ribosome’s.They are small organelles with no membrane, made up of RNA and proteins, with two
parts. They synthesize proteins.
Endoplasmic reticulum.It is a membrane system that forms a network of tubules and bags. There are two types:
- Rough: it has ribosomes on the outside of its membrane. It synthesizes and stores
proteins.
- Smooth: it has no ribosomes and it synthesizes, transports and stores fats and
destroys toxic substances.
Golgi apparatus.It is a membranous organelle formed by cisternaes. It is the organ that releases
substances out of the cell. All these substances go out go through the Golgi apparatus.
Lysosomes.They are small vesicles that contain digestive enzymes. They carry out the digestion of
large molecules or old organelles.
Mitochondria’s.They have a double membrane and produce energy through cell respiration.
Cytoskeleton.It is a group of protein filaments that form complex networks. They maintain the shape
of the cell and are involved in organelle movement in cell division.
Centrioles.They are two perpendicular cylinders formed by tubules that direct the movement of the
cilia and flagella and the movement of genetic material during cell division.
Cell wall.It is an external cover that protects and gives shape to the plant cell. It is made up of
cellulose.
Vacuoles.They are a group of vesicles wrapped by a membrane that store different substances.
They are more common in plant cells than in animal cells.
Chloroplasts.They are organelles with two membranes that contain chlorophyll, and produce organic
matter through photosynthesis.
Nucleus.A structure that contains the genetic material with the necessary information to direct
and control the cell function.
Characteristic of human being.Human beings are living things so:
- They perform the three vital functions: nutrition, relation and reproduction.
- They are composed of chemical elements called bioelements like C, H, O, N, P and
S.
- The bioelements make up biomolecules like carbohydrates, fats, proteins and
nucleic acid.
- They are made up of cells, eukaryotic cells and animal cells.
- Their nutrition is heterotrophic.
- Our body is a multicellular organism, so it is consists of many cells, which have
different structures and functions.
In multicelullar organisms, cells are grouped together to form tissue; Different types
of tissue are get together to form organs; Organs are grouped together to form
systems and systems are grouped together to form a human being.
Tissue.Tissue is a group of cells that have the same origin and carries out certain processes.
There are different types of tissues:
1. Protective tissue: epithelial tissue and mucosae:
- Epithelial tissue: it is the covering of the body, the skin.
- Mucosae: it protects the internal cavities (digestive and respiratory tracts).
2. Reserves: adipose tissues: The cells in adipose tissue accumulate fat.
3. Supporting the body:
- Bone tissue: it is rigid because it contains mineral salts.
- Cartilaginous tissue: it forms cartilages and tendons.
4. Secretion:
- Gland tissue produces and releases substances with different functions.
5. Connection:
- Connective tissue joins other tissue together and covers the organs.
6. Movement:
The cells in muscle tissue contract and relax, causing the body to move.
7. Communication:
- Nerve tissue coordinates the functions of all the organs
- Blood tissue: It transports substances inside the organism, it defends the organisms
and it takes part in the process of blood coagulation.
Organs.An organ is a group of several types of tissue that get together to perform the same
functions.
When different types of tissue join together and form organs, their functions complement
each other and produce more complex functions.
Some examples of organs in our body are the heart, stomach, lung, kidney, liver, etc.
Systems.They are formed by organs, and they are responsible for carrying out the functions of
nutrition, relation and reproduction.
Some systems are made up by different tissues and some systems are consist of only for
one type of tissue.
System for nutrition.Nutrition involves four systems:
1. Digestive system: this prepares food so that the cells can use it (digestion).
2. Respiratory system: It carries out the gassy exchange during breathing: it takes
oxygen and it takes away carbon dioxide.
3. Circulatory system: It transports substances inside the organism. It distributes
nutrients and oxygen to the cells and it picks up the waste substances produced by
cells.
4. Excretory system: This collects the substances produced by excretion and
discharges them outside the body. It also takes part in regulating the internal
environment.
System for reproduction.Reproduction assures our survival over time. This function involves both male and
female reproductive organs.
System for relation.Several systems and organs are involved in the reaction to stimuli:
- The sensory organs: these pick up information from the environment and send it to
the nervous system.
- The nervous system: this receives information from the sensory organs and works
out suitable responses. It coordinates all the bodily functions.
- The endocrine system: this is made up of certain organs (glands) that secrete
hormones that have different effects on our body.
- The skeletal system and the muscular system: these are responsible for a person’s
movement. They a re formed by bones and muscles respectively.