The document provides information on cells and their structures. It defines the cell as the basic unit of life and describes key cellular components including the cell membrane, cytoplasm, nucleus, organelles like mitochondria and lysosomes, and other structures. It also explains the process of mitosis and how cells divide to form two daughter cells. Additionally, it discusses the four main types of tissues - epithelial, connective, muscle and nervous tissue - and provides details on their characteristics and functions.

3. CELLS
 The cell is the basic structural, functional, and biological
unit of all known living organisms.
 They are often called the "building blocks of life”
 Mostly cells are microscopic (an average sized cell is
only one fifth the size of the smallest dot you can make
on a sheet of paper with a sharp pencil)
 Although they are minute, cells act as complex factories
to carry out the functions of life.

4. CELL STRUCTURE
Cell membrane
Cytoplasm
Nucleus
Endoplasmic reticulum (E.R)
Golgi apparatus
Mitochondria
Lysosomes
Plasmid
Vacuole
Ribosome
Centrioles

5. CELL MEMBRANE
 The cell membrane (also known as the plasma
membrane or cytoplasmic membrane) is a biological membrane that
separates the interior of all cells from the outside environment.
 It is selectively permeable to ions and organic molecules and
controls the movement of substances in and out of cells.
 The basic function of the cell membrane is to protect the cell from
its surroundings.
 The cell membrane also plays a role in anchoring
the cytoskeleton to provide shape to the cell, and in attaching to
the extracellular matrix and other cells to hold them together to
form tissues.

6. CYTOPLASM
 Basically cytoplasm is the substance that fills the cell.
 It is a jelly-like substance and it is made up of eighty
percent water and is usually clear and colourless.
 It serves as a molecular soup, it is in the cytoplasm
where all the cellular organelles are suspended and
are bound together by a lipid bilayer membrane.
 The peripheral zone of cytoplasm is thick and jelly-like
substance, known as the plasmogel. The surrounding
area of the nuclear zone is thin and liquefied in nature
and is known as the plasmosol
 The cytoskeleton of the cytoplasm provides shape to
the cell and it also facilitates movement. It forms a
framework for the movement of organelles around the
cytoplasm - most of the organelles are attached to the
cytoskeleton.

7. NUCLEUS
 The nucleus is a membrane bound structure that contains the
cell's hereditary information and controls the cell's growth
and reproduction.
 It is the command center of a eukaryotic cell and is
commonly the most prominent organelle in a cell.
 The nucleus is the largest cellular organelle in animal
cells. In mammalian cells, the average diameter of the nucleus
is approximately 6 micrometres (µm), which occupies about
10% of the total cell volume
 The viscous liquid within it is called nucleoplasm. It appears
as a dense, roughly spherical or irregular organelle.
 The nucleus controls many of the functions of the cell (by
controlling protein synthesis) and contains DNA (in
chromosomes).

8. ENDOPLASMIC RETICULUM (E.R)
 E R is a type of organelle in the
eukaryotic cells that forms an
interconnected network of
flattened, membrane-enclosed
sacs or tube-like structures known
as cisternae.
 The membranes of the ER are
continuous with the outer nuclear
membrane
 It is of two types; smooth
ER(absence of ribosome at outer
surface)and rough ER (presence of
ribosome at outer surface)

9. GOLGI APPARATUS
 The Golgi apparatus, also known as the Golgi complex, Golgi
body, or simply the Golgi, is an organelle found in
most eukaryotic cells
 The Golgi apparatus is a major collection and dispatch station
of protein products received from the endoplasmic reticulum
 A major function is the modifying, sorting and packaging of
proteins for secretion
 . It is also involved in the transport of lipids around the cell,
and the creation of lysosomes
 . The sacs or folds of the Golgi apparatus are called cisternae

10. MITOCHONDRIA
 The mitochondrion (plural mitochondria) is a
double membrane-bound organelle found in
all eukaryotic organisms, although some cells in some
organisms may lack them (e.g. Red blood cells)
 The main job of mitochondria is to perform cellular
respiration. This means it takes in nutrients from the cell,
breaks it down, and turns it into energy
 This energy is then in turn used by the cell to carry out
various functions
 Also known as power house of cell because they generate
most of the cell's supply of adenosine triphosphate (ATP),
used as a source of chemical energy.
 The number of mitochondria in a cell can vary widely
by organism, tissue, and cell type. For instance, red blood
cells have no mitochondria, whereas liver cells can have
more than 2000

11. LYSOSOMES
 A lysosome is a membrane-bounded organelle found in
most animal cells.
 They are spherical vesicles which contain hydrolytic
enzymes that can break down virtually all kinds
of biomolecules.
 It is One of the key organelles involved in digestion and
waste removal as hey contain digestive enzymes.
 the interior of the lysosomes is acidic compared to the
slightly basic cytosol

12. PLASMID
 A plasmid is a small DNA molecule within a
cell that is physically separated from
a chromosomal DNA and can replicate
independently
 They are most commonly found
in bacteria as small circular, double-
stranded DNA molecules; however,
plasmids are sometimes present
in eukaryotic organisms
 plasmids often carry genes that may benefit
the survival of the organism, for
example antibiotic resistance
 plasmids usually are very small and contain
only additional genes that may be useful to
the organism under certain situations or
particular conditions
 . Plasmids are much used in the laboratory
manipulation of genes.

13. VACUOLE
 A vacuole is a membrane-bound organelle which is present
in all plant and fungal cells and some protest,
animal and bacterial cells
 Vacuoles are essentially enclosed compartments which are
filled with water containing inorganic and organic molecules
including enzymes in solution
 Vacuoles are formed by the fusion of multiple
membrane vesicles and are effectively just larger forms of
these.
 It has no basic shape or size; its structure varies according to
the needs of the cell.
 It is surrounded by a membrane and functions to hold
materials and wastes
 . It also functions to maintain the proper pressure within the
plant cells to provide structure and support for the growing
plant

14. RIBOSOME
 The ribosome is a complex molecular machine,
found within all living cells, that serves as the
site of biological protein synthesis
 Ribosomes link amino acids together in the
order specified by messenger RNA(mRNA)
molecules.
 Ribosomes can be found floating within the
cytoplasm or attached to the endoplasmic
reticulum

15. CENTRIOLE
 a centriole is a cylindrical cell
structure composed mainly of a
protein called tubulin that is found in
most eukaryotic cells.
 Centrioles are involved in the
organization of the mitotic
spindle and in the completion of
cytokinesis
 The position of the centriole
determines the position of the
nucleus and plays a crucial role in the
spatial arrangement of the cell.
 The main function of the centriole is
to help with cell division in animal
cells

16. MITOTIC CELL DIVISION

17. INTERPHASE
 Interphase is the phase of the cell cycle in
which a typical cell spends most of its life.
 During this phase, the cell copies its DNA in
preparation for mitosis
 There are three phases in interphase
 G (Gap 1), in which the cell grows and
functions normally. During this time, a high
amount of protein synthesis occurs and the
cell grows (to about double its original size) -
more organelles are produced and the volume
of the cytoplasm increases.
 Synthesis (S), in which the cell duplicates its
DNA
 G2 (Gap 2), in which the cell resumes its
growth in preparation for division. The
mitochondria divide and the cell continues to
grow until mitosis begins

18. PROPHASE
 In this phase, the
chromosomes condense and
thicken
 Each duplicated
chromosome appear as two
identical sister chromatids
 The mitotic spindle begins to
form.

19. METAPHASE
 In metaphase, the centromeres of the
chromosomes convene themselves on
the metaphase plate

20. ANAPHASE
 The spindle fibers begin to
contract
 This starts to pull the sister
chromatids spart
 At the end of anaphase a
complete set of daughter
chromosomes is found in each
pole

21. TELLOPHASE AND CYTOKINESIS
 During telophase, the effects
of prophase and prometaphase (the
nuclear membrane
and nucleolus disintegrating) are
reversed.
 Two daughter nuclei form in each
daughter cell
 The chromosomes reach the poles as
the nuclear membranes re-form
around each set of chromatids,
the nucleoli also reappear

23. TISSUE
 tissue is a cellular organizational level intermediate
between cells and a complete organ.
 is an ensemble of similar cells from the same origin that
together carry out a specific function.
 The study of tissue is known as histology

24. TYPES OF TISSUE
CONNECTIVE TISSUE
CONNECTIVE TISSUE
PROPER
LOOSE
DENSE
FLUID CONNECTIVE
TISSUE
BLOOD
LYMPH
SUPPORTING
CONNECTIVE TISSUE
CARTILAJE
BONE
MUSCLE TISSUE
SMOOTH
MUSCLE
SKELETAL
MUSCLE
CARDIAC
MUSCLE
EPITHELIAL
TISSUE
SQUAMOUS
EPITHELIUM
CUBOIDAL
EPITHELIUM
COLUMNAR
EPITHELIUM
TRANSITIONAL
EPITHELIUM
NERVOUS
TISSUE

25. EPITHELIAL TISSUE
 Epithelial tissues line the cavities and surfaces of blood
vessels and organs throughout the body.
1.

26. EPITHELIAL TISSUE
SQUAMOUS EPITHELIUM
 It has surface whose outermost (apical) layer
consists of thin, flat cells.
 they may be composed of one layer of cells, in
which case it is referred to as simple squamous
epithelium, or it may possess multiple layers,
referred to then as stratified squamous epithelium.
 squamous epithelial cells have
a polygonal appearance when viewed from above
CUBOIDAL EPITHELIUM
 cuboidal epithelia are epithelial cells having a
cube-like shape; that is, their width is
approximately equal to their height.
 They may exist in single layers (simple cuboidal
epithelium) or multiple layers (stratified cuboidal
epithelium) depending on their location (and thus
function) in the body.

27. EPITHELIAL TISSUE
COLUMNAR EPITHELIUM
 Columnar epithelial cells are epithelial
cells whose height are at least four times their
width.
 Columnar epithelia are divided into simple (or
unilayered), and stratified (or multi-layered)
 They are found in the inner lining of the
intestine. They secrete digestive enzymes and
absorb digested food.
TRANSITIONAL EPITHELIUM
 Transitional epithelium is a type of tissue consisting
of multiple layers of epithelial cells which can
contract and expand.
 This tissue structure type is found in urothelium,
including that of the urinary bladder, the ureters,
and the superior urethra and gland ducts of
the prostate.
 They also functions as barrier between the lumen,
or inside hollow space, of the tract that it lines and
the bloodstream.

28. CONNECTIVE TISSUE
 The different types of connective tissue maintain the form of organs throughout the body
 Connective tissues provide a matrix that supports and physically connects other tissues
and cells together in organs

29. CONNECTIVE TISSUE
CONNECTIVE TISSUE PROPER
it is categorised into two:
1) Loose:
 includes areolar tissue, reticular tissue,
and adipose tissue
 It holds organs in place and
attaches epithelial tissue to other underlying
tissues
 It may be found in tissue sections from
almost every part of the body
2) DENSE:
 also called dense fibrous tissue
 is a type of connective tissue with fibers as its
main matrix element
 forms strong, rope-like structures such
as tendons and ligament
FLUID CONNECTIVE TISSUE
It is categorised into two:
1) BLOOD
 Blood is considered a connective tissue for two
basic reasons: (1) embryologically, it has the same
origin (mesodermal) as do the other connective
tissue types and (2) blood connects the body
systems
 The cell found in greatest abundance in blood is
the erythrocyte, responsible for transporting
oxygen to body tissues
2) LYMPH
 Lymph is a clear fluid that is similar to plasma but
contains less protein
 It flows through lymphatic vessels throughout the
body and includes chemicals and cells whose
composition varies according to location within
the body.

30. SUPPORTING CONNECTIVE TISSUE
It is categorised into two:
CONNECTIVE TISSUE
1) CARTILAJE
 Cartilage is a resilient and
smooth elastic tissue, covering and
protecting the ends of the
long bones at joints, and is a structural
component of the rib cage, the ear,
the nose, the bronchial tubes,
the intervertebral discs, and many more
other body components
 It is not as hard and rigid as bone, but
it is stiffer and less flexible than muscle
2) BONE
 Bone tissue is the major structural and
supportive connective tissue of the
body
 Bone tissue forms the rigid part of
the bones that make up the skeleton.
 Supports muscles, organs, and soft
tissues.
 It is formed by cells, called osteoblasts

31. MUSCLE TISSUE
 Muscle tissue is a soft tissue that composes muscles in animal bodies, and
gives rise to muscles' ability to contract
 It is formed during embryonic development through a process known
as myogenesis
 Muscle tissue varies with function and location in the body

32. MUSCLE TISSUE
SMOOTH MUSCLE
 Smooth muscle is an involuntary
non-striated muscle
 Smooth muscle is found within
the walls of blood vessels
 Smooth muscle is also found in
lymphatic vessels, the urinary
bladder, uterus, male and
female reproductive
tracts, gastrointestinal tract,
respiratory tract, the ciliary
muscle, and iris of the eye
SKELETAL MUSCLE
 It is a form of striated muscle tissue which
is under the voluntary control of
the somatic nervous system
 Most skeletal muscles are attached
to bones by bundles of collagen fibers
known as tendons
 Muscle fibres, or muscle cells, are formed
from the fusion of
developmental myoblasts in a process
known as myogenesis

33. MUSCLE TISSUE
CARDIAC MUSCLE
 Cardiac muscle (heart muscle) is an involuntary, striated
muscle that is found in the walls and histological
foundation of the heart, specifically the myocardium
 These three types of muscle all form in the process
of myogenesis
 The myocardium is the muscle tissue of the heart, and
forms a thick middle layer between the
outer epicardium layer and the inner
endocardium layer.
 Cardiac muscle cells, unlike most other tissues in the
body, rely on an available blood and electrical supply
to deliver oxygen and nutrients and remove waste
products such as carbon dioxide

34. NERVOUS TISSUE
 Nervous tissue or nerve tissue is the
main tissue component of the two parts of the nervous
system; the brain and spinal cord of the central
nervous system (CNS), and the branching peripheral
nerves of the peripheral nervous system (PNS), which
regulates and controls bodily functions and activity
 The function of nervous tissue is to form the
communication network of the nervous system by
conducting electric signals across tissue
 It is composed of neurons, or nerve cells, which
receive and transmit impulses