Cell physiology

1. By Gladys Stephen

2. Cell-Introduction
 Smallest functional units of the body
 Grouped together to form tissues, each having a specialized function, e.g.
blood, muscle, bone.
 Different tissues are grouped together to form organs, e.g. heart, stomach,
brain.
 Organs are grouped together to form systems, that perform particular
function that maintains homeostasis and contributes to the health of the
individual. E.g. digestive system, cardiovascular system.
By Gladys Stephen

3. TISSUE
 Tissue is defined as the group of cells having similar function. There
are many types of tissues in the body.
 classified into four major types
 primary tissues that includes
 Muscle tissue (skeletal muscle, smooth muscle and cardiac
muscle)
 Nervous tissue (neurons and supporting cells)
 Epithelial tissue (squamous, columnar and cuboidal epithelial
cells)
 Connective tissue (connective tissue proper, cartilage, bone
and blood).
By Gladys Stephen

4. ORGAN
 a structure that is formed by two or more primary types of tissues, do a
physiological function.
 Some organs are composed of all the four types of primary tissues.
 The organs are of two types, namely
 tubular/hollow organs
 compact or parenchymal organs.
 Some of the organs in the body are brain, heart, lungs, stomach,
intestine, liver, gallbladder, pancreas, kidneys, endocrine glands,
etc
By Gladys Stephen

5. SYSTEM
 A group of organs that work together to carry out specific functions of the body.
 Each system performs a specific function.
 digestive system is concerned with digestion of food particles.
 Excretory system eliminates unwanted substances.
 Cardiovascular system is responsible for transport of substances between the
organs.
 Respiratory system is concerned with the supply of oxygen and removal of carbon
dioxide.
 Reproductive system is involved in the reproduction of species. Endocrine system
is concerned with growth of the body and regulation and maintenance of normal
life.
 Musculoskeletal system is responsible for stability and movements of the body.
 Nervous system controls the locomotion and other activities including the
intellectual functions.
By Gladys Stephen

6. The cell
 A cell consists of a cell (plasma) membrane inside which a
nucleus and cytoplasm surrounding the nucleus is present
 Organelles are small organs of the cell embedded in the
cytoplasm.
 Have individual and highly specialized functions
 Organelles are enclosed in their own membrane within the
cytoplasm.
 Individual cells are too small to be seen through the naked
eye.
By Gladys Stephen

7. By Gladys Stephen

8. Cell (Plasma) membrane
 Also called as plasmalemma
 Separates outside fluid
(extracellular fluid) and the
intracellular fluid
 It is a semipermeable
membrane
 The thickness of the cell
membrane varies from 75-
111A
By Gladys Stephen

9. Cell membrane
 Consists of 2 layers of
phospholipids with protein and
sugar molecule embedded in
them.
 Those proteins molecules extend
all the way through the membrane
provides channels that allow the
passage of e.g. electrolytes and
non-lipid substances
By Gladys Stephen

10. Membrane proteins
 The lipid bilayer forms the basis of
the cell membrane, distributed
throughout with various proteins.
 Two different types of proteins
that are commonly associated with
the cell membrane
 Integral proteins – embedded in
the membrane e.g. cell adhesion
protein.
 peripheral protein - selectively
allows particular materials, such as
certain ions, to pass into or out of
the cell., e.g. channel protein
By Gladys Stephen

11.  Functions of membrane protein
 Cell membrane protects the cytoplasm and the organelles
present in the cytoplasm
 Cell membrane acts as a semipermeable membrane, which
allows only some substances to pass through it and acts as a
barrier for other substances
 Nutrients are absorbed into the cell through the cell membrane
 Metabolites and other waste products from the cell are excreted
out through the cell membrane
 Oxygen enters the cell from the blood and carbon dioxide
leaves the cell and enters the blood through the cell membrane
(exchange of gases)
 Cell membrane is responsible for the maintenance of shape and
size of the cell.
By Gladys Stephen

12. Cytoplasm
 Cytoplasm of the cell is the jellylike material formed by 80% of water.
 It contains a clear liquid portion called cytosol and various particles of
different shape and size.
 These particles are proteins, carbohydrates, lipids or electrolytes in nature.
 Cytoplasm contains many organelles with distinct structure and function.
 Cytoplasm is made up of two zones:
 Ectoplasm: Peripheral part of cytoplasm, situated just beneath the cell
membrane
 Endoplasm: Inner part of cytoplasm, interposed
By Gladys Stephen

13. The organelles in the cytoplasm are:
 Nucleus
 Mitochondria
 Ribosomes
 Endoplasmic reticulum
 Golgi apparatus
 Lysosomes
 Peroxisome
 Centrosome and centrioles
 Secretory vesicles
 cytoskeleton
By Gladys Stephen

14.  Nucleus
 Every cell has a nucleus (except matured erythrocyte).
 Nucleus is the largest organelle inside a nuclear envelope (10-20
micron)
 Nucleus contains body’s genetic material (gene)
 The cells with nucleus are called
 eukaryotes – cell with nucleus
 Prokaryote - cell without nucleus
 Nucleolus is present within the nucleus which involves in the
manufacture or synthesis and assembly of the components of
ribosomes.
By Gladys Stephen

15. Mitochondria
 Mitochondria are membranous,
sausage-shaped structures in the
cytoplasm
 It is called as power house of the
cell
 Involves in aerobic respiration
(energy is made available in cell)
by synthesizing ATP
 Most active cell types have the
greater number of mitochondria
e.g. liver, muscle
By Gladys Stephen

16. ribosomes
 Tiny granules composed of RNA
and protein
 Present on the outer surface of the
nuclear envelope and rough
endoplasmic reticulum
 Make proteins for use within the
cell such as enzymes required for
metabolism
By Gladys Stephen

17. Endoplasmic reticulum
 Interconnecting membranous
canals in the cytoplasm
 Two types
 Smooth ER – synthesizes lipids
and steroid hormones, and
associated with the detoxification
of some drugs.
 Rough ER – Studded with
ribosomes and are site of synthesis
of some proteins.
By Gladys Stephen

18. Golgi apparatus
 Consists of stacks of closely folded
flattened membranous sacs
 Proteins move from ER to GA
where they are packed into
membrane-bound vesicles called
secretory granules.
 These vesicles move to the plasma
membranes and fuse with it, when
in need
 The contents then leave the cell by
exocytosis
By Gladys Stephen

19. lysosomes
 Type of secretory vesicle with membranous walls formed by
GA.
 Contain a variety of enzymes involved in breaking down
fragments of organelles and large moleculs (RNA, DNA,
carbohydrates, proeins) inside the cell in to smaller particle
 Lysosomes in WBC contain enzymes that digest foreign
material such as microbes
By Gladys Stephen

20. cytoskeleton
 Consists of an extensive network of tiny protein fibers
 Microfilaments
 Smallest fibers
 Provides structural support
 Maintains characteristic shape of cell
 Permits contraction e.g. muscle cells
 Microtubules
 Larger contractile protein fibers that are involved in the movement of
 Organelles within the cells
 Chromosomes during cell division
 Cell extensions
By Gladys Stephen

21.  Centrosomes
 Directs organization of microtubules within the cell.
 Consists of a pair of centrioles
 Plays an important role in cell division
 Cell extensions
 Project from the plasma membrane
 Main components are microtubules which allow movement
 Types of cell extensions are
 Microvilli – tiny projections containing microfilaments
 Cilia – microscopic hair-like projections containing microtubules along the border of
cells.
 Flagella – single, long whip-like projections containing microtubules forming tails of
cells like spermatozoa
By Gladys Stephen

22. Cell cycle
 The period between two cell divisions is known as the cell cycle.
 Has two phases that can be seen on light microscopy
 Mitosis (M phase)
 Interphase
 longer phase and 3 separate stages are recognized .
 First gap phase (G1) – the cell grows in size and volume.
 Synthesis of DNA (S phase) – the chromosomes replicate forming two identical copies
of DNA. Therefore following this phase, the cell now has 92 chromosomes enough DNA
for 2 cells and ready to divide by mitosis
 Second gap phase (G2) - further growth and preparation for cell division.
By Gladys Stephen

23.  Mitosis
It is a continuous process involving 4 stages seen by light microscopy
 Prophase
 Replicated chromatin becomes tightly coiled (seen under microscope)
 46 chromosomes is paired with its copy in a double chromosome unit
 2 chromotids joined to each other at the centromere
 Mitotic apparatus appears – containing 2 centrioles separated by mitotic spindle
 Nuclear envelope disappears.
 Metaphase
 Chromatids align on the centre of the spindle, attached by their centromeres
 Anaphase
 Centromeres separate, each pair of sister chromatids (chromosomes) migrates to each end of
the spindle
 Telophase
 Mitotic spindle disappears, chromosomes uncoil
 Nuclear envelope reforms
By Gladys Stephen

24. Transport of substances across cell membranes
 Passive transport
 Diffusion
 Faciliated diffusion
 Osmosis
 Active transport
 The sodium-potassium pump
 Bulk transport
By Gladys Stephen

25.  Passive transport
 When substances can cross the semipermeable plasma and organelle
membranes and does not require any energy.
 Move down the concentration gradient without using energy
 Diffusion
 Small molecules diffuse down the concentration gradient
 Lipid-soluble materials – oxygen, carbon dioxide, fatty acids and steroids cross the
membrane by dissolving in the lipid part of membrane
 Water-soluble materials – sodium, potassium and calcium cross the membrane by
passing through water-filled channels
By Gladys Stephen

26. Different types of cells in the body
(BASED ON TISSUE FORMATION)
 Bone cells (Osteocytes)
 Cartilage cells (chondrocytes)
 Nerve cells
 Epithelial cell
 Secretory cell
 Adipose cells
 Blood cells
By Gladys Stephen

27. TYPES OF CELLS IN HUMAN BODY
(BASED ON THEIR FUNCTION)
 Conductive cells
 Connective cells
 Glandular cells
 Storage cells
 Supportive cells
By Gladys Stephen

28.  Special types of cells are
 Sperms
 Oocytes
 Stem cells
 Rods and cones
 Ciliated cells
 Blood cells
By Gladys Stephen