CELLS, TISSUES & ORGANS

CELLS• The basic functional unit of body structure is the cell.• Cells require food, H2O, and O2 to live and perform their

functions.• Each cell has the same basic parts, however, their size, shape

and function may vary.• Each cell has 3 main parts

1. Nucleus • This is the control centre of the cell and contains the DNA

(deoxyribonucleic acid). • DNA contains the “blueprints” for building the whole human

body, specifically proteins. • DNA is also necessary for cell reproduction.

CELLS• The nucleus contains 3 regions:

1. Nuclear membrane – a double membrane barrier that is selectively permeable. The nuclear membrane encloses a jelly like substance called nucleoplasm which contain the nucleoli and chromatin.

2. Nucleoli– this where ribosomes are made. Ribosomes are the sites for protein synthesis

3. Chromatin – a loose network of bumpy threads that form chromosomes. Each cell has 46 chromosomes that contain genes. Genes control the physical and chemical traits that are inherited from parents.

CELLS2. Cytoplasm • the cytoplasm is outside of the nucleus and inside the plasma

membrane, it contains many smaller structures that perform cell functions including the organelles.

ORGANELLES• Organelles are little organs, each performing their own function

within the cell.• Ribosomes – tiny, dark, round bodies made of protein. They are the

sites of protein synthesis• Endoplasmic reticulum (ER)– is a network within the cell. A

system of fluid filled tubules that make up half the cells membranes. They carry substances from one part of the cell to another. There is Rough ER and Smooth ER

CELLS• Golgi Apparatus – looks like a stack of flattened

membranous sacs. It is the “traffic director” for cellular proteins. Its main function is to modify and package proteins.

• Lysosomes – The cells “demolition site”. They digest non-useable cell structures and foreign substances.

• Peroxisomes – membranous sacs that detoxify harmful or poisonous substances. Their most important is to disarm free radicals (highly reactive chemicals)

• Mitochondria – sausage shaped. The “powerhouse” of the cell. They are responsible for producing/supplying energy to the cell

CELLS• Cytoskeleton – The cell’s “bones and muscles”. It gives

the cell shape• Centrioles – The paired centrioles are rod shaped bodies.

They move substances along the cell surface using cilia.

3. The Plasma Membrane• A fragile, transparent barrier that contains the cell contents and

separates them from the surrounding environment.

CELLSNUCLEUS

• Nuclear membrane• Nucleoli• Chromatin

CYTOPLASM• Ribosomes• Endoplasmic

reticulum• Golgi apparatus• Lysosomes• Peroxisomes• Mitochondria• Cytoskeleton• Centrioles

PLASMA MEMBRANE

CELLSCell Division – Mitosis & Cytokinesis• Mitosis is division on the cell’s nucleus• There are 4 stages of mitosis

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase• Cytokinesis – division of the cytoplasm. Begins

during late anaphase and completes during telophase

TISSUES

TISSUES• Groups of cells that are similar in structure and

function are called tissues.

The 4 primary tissue types are:

1. Epithelium - covering

2. Connective tissue - support

3. Nervous tissue - control

4. Muscle tissue - movement

TISSUESEPITHELIUM• The lining, covering and glandular tissue of the body.• Epithelial functions include:

1. Protection – protects against bacterial/chemical damage

2. Absorption – lines some of the digestive system (stomach, small intestine) which absorb food.

3. Filtration - kidneys

4. Secretion – speciality of the glands, which produce sweat, oil, digestive enzymes and mucous

• Epithelial cells fit closely together and forms sheets• Epithelial cells have no blood supply, they rely on connective tissue

for food and O2

• Epithelial cells regenerate themselves easily

TISSUESCONNECTIVE TISSUE• Connective tissue connects body parts• It is found everywhere in the body and is the most abundant

and widely distributed type of tissue.• Most connective tissue has a good blood supply, however,

tendons and ligaments have a very poor blood supply, and cartilage has no blood supply.

• The extracellular matrix is what gives the connective tissue its strength. Depending on the type of connective tissue, the matrix may be liquid, semi-solid, gel like or very hard.

• The main functions of connective tissue are:• Protecting, supporting and binding together.

TISSUESTYPES OF CONNECTIVE TISSUE• From most rigid to softest:

• Bone – Very hard matrix, protects and supports organs• Cartilage – less hard and more flexible than bone. There

are 3 types:

1. Hyaline cartilage – rubbery, forms the larynx, attaches the ribs to the breastbone, and covers the ends of bones where they form joints

2. Elastic cartilage – elastic and flexible. The ear

3. Fibrocartilage – forms cushionlike discs between the vertebrae of the spinal column

TISSUES• Dense connective tissue– forms strong rope like

structures such as tendons, ligaments, and skin• Loose connective tissue – soft tissue. 3 types

1. Areolar tissue – soft tissue that cushions, protects, and holds organs in place

2. Adipose tissue – is fat. Forms subcutaneous tissue beneath the skin. Insulates and protects the body.

3. Reticular connective tissue - internal framework for lymph nodes, spleen, and bone marrow

• Blood – considered a connective tissue because it has blood cells and plasma.

TISSUESNERVOUS TISSUE• Nervous tissue is made up of neurons• Neurons receive and conduct electrochemical impulses

from one part of the body to another.• Neurons along with supporting cells,

• Insulate• Support • Protect and• Make up the nervous system

TISSUESMUSCLE TISSUE• Muscles tissues are specialized to contract or shorten to produce

movement• There are 3 types of muscle tissue

1. Skeletal muscle – packaged into sheets which are attached to the skeleton and are controlled voluntarily. When skeletal muscles contract, they pull on bones or skin which causes movement.

2. Cardiac muscle – only found in the heart. When it contracts, the heart acts like a pump. Cardiac muscle is involuntary.

3. Smooth muscle – found in the stomach, bladder, uterus and blood vessels. When it contracts the organ either constricts or dilates.