Download 2. ANIMAL CELLS AND TISSUES Objectives After completing this

2. ANIMAL CELLS AND TISSUES
Objectives
After completing this exercise you should be able to
1. Understand the cell theory and the basic structure of an animal cell.
2. Differentiate between prokaryotic and eukaryotic cells.
3. Relate the concepts of cells, tissues, organs, organ systems and organisms.
4. List the four basic types of tissues with examples.
5. Identify and describe the four tissues types and their subtypes.
Introduction
Animals are composed of cells and are organized in hierarchical levels. The study of the
complex form and function of animal body begins with the understanding of cells, tissues
and organs. The structure called as “cell”, was so named and first observed by Robert
Hooke through his modified microscope.
The cell is the structural and fundamental unit of life. The cell theory was developed much
later in nineteenth century by a botanist Matthias Schleiden, and a zoologist Theodor
Schwann. A group of similar cells carrying out common functions make a tissue. Different
tissues combine together make an organ, while various organs make a system; systems, in
turn, form an organism.
Cell Theory
The cell theory is summarized as follows:
1) All organisms are composed of cells.
2) All cells derive from previously existing cells.
3) Cells carry out all the vital functions of the organism.
4) Cells contain hereditary material that regulates cell functions and which is passed on
to the next generation of cell.
Cell Structure
A
typical animal cell has a cell membrane that encloses the cytoplasm and a well defined
nucleus. The nucleus houses DNA, the hereditary material. The cytoplasm contains of
membrane bound organelles like endoplasmic reticulum, Golgi apparatus, mitochondria,
vacuoles, ribosome’s and lysosomes. The size of a cell is determined by the ratio of its cell
surface to its volume that decides its transporting efficiency.
Cell Types
1) Prokaryotic cells
.
2) Eukaryotic cells
Plant cells
Animal cells
TYPES OF CELLS
Prokaryotic cells
Eukaryotic cells
•
Means “before nucleus”
•
Means “true nucleus”
•
Do not have a nucleus
•
Have a membrane-bound nucleus
•
Without membrane- bound organelles
•
Have membrane- bound organelles
•
Do not have cytoskeleton of
microfilaments and microtubules
•
Cytoskeleton made of microfilaments and
microtubules
•
Are very small in size
•
Are comparatively bigger in size
•
Eg. Domain Eubacteria and Archaea
•
Eg. Domain Eukarya – Animal cells
Animal Cell Structure
A typical animal cell has a cell membrane, hereditary material in the nucleus; cytoplasm
along with organelles and membrane bound structures.
Figure 1: Animal Cell
EXERCISE
Animal cells:
I] IDENTIFICATION OF CELL PARTS
1. Using figure 1 and the models study the organelles of an animal cell.
2. Make a list of structures you identify in the model.
II] PREPARATION OF STAINED WET MOUNT
1. Take a slide with a small drop of methylene blue.
2. Scrape the inner lining of your cheek using a toothpick and roll it in the drop of
methylene blue.
3. Place a cover slip over it, and observe under scanning, low power and high power lenses
of compound microscope; sketch below.
Scanning Lens
Low Power Lens
High Power Lens
Animal tissues:
Tissue is a group of similar cells specialized for a common function.
The four basic types of tissues are A) Epithelial
B) Connective
C) Muscle
D) Nervous
A) Epithelial Tissue: A sheet of cells that line the surface of the structures in the body.
Functions:
1)Absorption – intestine
2)Transportation – kidney tubules
3)Excretion – sweat glands
4)Protection – skin
5)Sensory Reception – tongue
The classification of Epithelial Tissue is made on the basis of1) Number of layers
2) Shape of cells
1) Number of layers – i) Simple – A single layer of cells.
ii) Stratified – Two or more layers of cells.
I
iii) Pseudostratified – Single layered, but appears to be two layered
i) Simple – Single layer of cells, eg. Blood Vessels
Observe
Sketch
ii) Stratified – Two or more layers of cells, eg. Lining of the oesophagus
Observe
Sketch
iii) Pseudostratified – Single layered, but appears to be two layered, eg. Tracheal lining
Observe
Sketch
2) Shape of cells – i) Squamous – Thin flattened cells.
ii) Cuboidal – Cube like cells .
I
iii) Columnar – Elongated and column shaped
i) Squamous – Thin flattened cells, eg. Vagina
Observe
Sketch
ii) Cuboidal – Cube like cells, eg. Thyroid gland
Observe
Sketch
iii) Columnar – Elongated cells, eg. Stomach
Observe
Sketch
B) Connective Tissue: Is found throughout the body and has three main components
cells, fibers and extracellular matrix.
Functions:
1)Support – loose , fibrous, bone and tendon
2)Shock absorber – cartilage , adipose
3)Storage and Protection – adipose
4)Transportation – blood
Types of connective tissue 1) Loose connective tissue
2) Fibrous connective tissue
3) Bone
4) Cartilage
5) Adipose
6) Blood
1) Loose connective tissue, eg. Areolar tissue
Observe
Sketch
2) Fibrous connective tissue, eg. Tendon
Observe
Sketch
3) Bone
Observe
Sketch
4) Cartilage
Observe
Sketch
5) Adipose:
Observe
Sketch
6) Blood
Observe
Sketch
C) Muscle Tissue: Muscle cells contain contractile filaments that move past each other and
change the size of the cell.
Functions:
1)Movement - Cells contract and relax and bring about movement of the structures to
which they are attached.
Types: They are of three main types
1) Smooth
2) Skeletal
3) Cardiac
1) Smooth, eg. stomach
Observe
Sketch
2) Skeletal, eg. attached to bones
Observe
Sketch
3) Cardiac, eg. heart wall
Observe
Sketch
D) Nervous Tissue: Regulates and controls body functions. It is found in brain, spinal cord
and nerves.
Types and Functions: Nervous tissue is composed of two types of cells.
1) Neurons - Conduction of impulse
2) Neuroglia cells - Nourishment and protection
Observe
Neurogliacells
Sketch
Neurons