Human Body
Structure and
Function 1
Book lists:
1. Guyton and Hall Textbook of Medical Physiology
2. Seeley’s Essentials of Anatomy and Physiology
3. Ganong’s Review of Medical Physiology
4. Fundamentals of Anatomy and Physiology
By Martini
1
,1. General Anatomy and General Physiology
Anatomy: Anatomy is the scientific discipline that investigates the body’s structures – for example, the shape and size
of the bones. In addition, anatomy examines the relationship between the structure of a body part and its function.
Thus, the fact that bone cells are surrounded by a hard, mineralized substance enables the bones to provide strength
and support. Understanding the relationship between structure and function makes it easier to understand and
appreciate anatomy.
Physiology: Physiology is the scientific investigation of the processes or functions of living things. The major goals
when studying human physiology are to understand and predict the body’s responses to stimuli and to understand how
the body maintains conditions within a narrow range of values in a constantly changing environment.
Organization of human body: Skeleton, skeletal muscular system
Skeletal system: The organ system of the body, formed mainly by the combination of bones and cartilages to form the
internal framework of the body, to give the definite shape of the body and to protect the inner soft visceral organs from
external pressure and shock is called skeletal system. This system also includes the hard integumentary derivatives like
hairs, furs and nails etc.
Functions:
1. Formation of framework: Bone forms the strong and rigid endoskeleton or framework of the body and support
the body.
2. Protection: The skeleton protects certain vital internal organs such as brain, heart, lungs, liver, spinal cord etc.
3. Connecting area of muscles and ligament: It provides area for attachment of muscles and ligaments.
4. Formation of lever system: Bones forms a system of levers that multiply the forces generated during the
connection of skeletal muscles and transform them into bodily movement.
5. Locomotion: The contraction of skeletal muscles create the movement of the bones. By such the movement
of the muscles of the legs, bipedal locomotion in man is completed.
6. Formation of blood corpuscles: In infants, the blood corpuscles are produced from the red bone marrow of
all bones. In adults, the blood corpuscles are produced in the bone marrow of only the cranium, ribs, sternum,
vertebrae and heads of the humerus and femur. The red bone marrow produces the RBC and hemoglobin.
WBC are also produced from the bone marrow.
7. Defense: The bone marrow also acts as a defensive agent of the body and also takes part in the re-orientation
of the bones.
8. Storage: It serves as a reservoir of calcium, phosphate and other ions and supply them to the blood whenever
necessary.
9. Poison inhibitor: It stores led, arsenic etc. and thus prevents the body from poisonous activity.
10. Destruction: The bone marrow sometimes destroy RBC if necessary.
11. Hearing and breathing: The skeleton helps in many physiological processes. The ear ossicles help in hearing;
the sternum and ribs in breathing.
Tissues, skin and appendages
Tissue: Tissues are groups of cells that have a similar structure and act together to perform a specific function.
Types of animal tissue:
1. Epithelial tissue
2. Connective tissue
3. Muscular tissue and
4. Nervous tissue
They are discussed below:
2
,Epithelial tissue: The tissue which constitutes the outer lining of the body or any internal organ is called epithelial
tissue.
Major features:
1. Mostly composed of cells: Epithelial tissue consists almost entirely of cells, with very little extracellular matrix
between them.
2. Covers body surfaces: Epithelial tissue covers body surfaces and forms glands that are derived
developmentally from body surfaces. The body surfaces include the exterior surface, the lining of the digestive
and respiratory tracts, the heart and blood vessels and the linings of many body cavities.
3. Distinct cell surfaces: Most epithelial tissues have one free or apical surface where cells are exposed and not
attached to other cells. The cells have a lateral surface where cells are attached to other epithelial cells. At the
base of the cells is basal surface attached to a basement membrane. The free surface often lines the lumen of
ducts, vessels and cavities. The basement membrane is a specialized type of extracellular material secreted by
epithelial and connective tissue cells. The basement membrane helps attach the epithelial cells to the underlying
tissues, like the adhesive on Scotch tape. It plays an important role in supporting and guiding cell migration
during tissue repair. The basement membrane is typically porous, which allows substances to move to and
from the epithelial tissue above it. A few epithelial tissues, such as those in lymphatic capillaries and liver
sinusoids, do not have basement membranes, and some epithelial tissues, such as those in some endocrine
glands, do not have a free surface or a basal surface with a basement membrane.
4. Cell and matrix connections: Specialized cell contacts bind adjacent epithelial cells together and to the
extracellular matrix of the basement membrane.
5. Nonvascular: Blood vessels in the underlying connective tissue do not penetrate the basement membrane to
reach the epithelium; thus, all gases and nutrients carried in the blood must reach the epithelium by diffusing
the from blood vessels across the basement membrane. In epithelial tissues with many layers of cells, diffusion
must also occur across the cells, and the most metabolically active cells are close to the basement membrane.
6. Capable of regeneration: Epithelial tissue has the ability to replace damaged cells with new epithelial cells.
Undifferentiated cells (stem cells) continuously divide and produce new cells. In some types of epithelial
tissues, such as those in the skin and digestive tract, new cells continuously replace cells that die.
Functions:
1. Protecting underlying structures: For example, the outer layer of the skin and the epithelium of the oral cavity
protect the underlying structures from abrasion.
2. Acting as a barrier: Epithelium prevents many substances from moving through it. For example, the skin acts
as barrier and reduces water loss from the body. The skin also prevents many toxic molecules and
microorganisms from entering the body.
3. Permitting the passage of substances: Though epithelium acts as a barrier for some substance, it also permits
many other substances to move through it. For example, O2 and CO2 are exchanged between the air and blood
by diffusion through the epithelium in the lungs. Epithelium acts as a filter in the kidney, allowing many
substances to pass from the blood into the urine but retaining other substances, such as blood cells and proteins
in the blood.
4. Secreting substances: Mucus glands, sweat glands and the enzyme-secreting portions of the pancreas are all
composed of epithelial cells that secrete their products onto surfaces or into ducts that carry them to other areas
of the body.
5. Absorbing substances: The plasma membranes of certain epithelial tissues contain carrier proteins, which
regulate the absorption of materials.
Classification:
A. Based on the number of cell layers in each:
1. Simple epithelium: It consists of a single layer of cells, with each cell extending from the basement
membrane to the free surface.
2. Stratified epithelium: It consists of more than one layer of cells, but only the basal layer attaches the
deepest layer to the basement membrane.
3. Pseudostratified columnar epithelium: It is a special type of simple epithelium. The prefix pseudo
means false, so this type of epithelium appears to be stratified but is not. It consists of one layer of
cells, with all the cells attached to the basement membrane. These appear to be two or more layers of
3
, cells because some of the cells are tall and extend to the free surface, whereas others are shorter and
do not extend to the free surface.
B. Based on idealized shapes:
1. Squamous: Squamous cells are flat or scalelike.
2. Cuboidal: They are cube-shaped; about as wide as they are tall.
3. Columnar: Columnar cells tend to be taller than they are wide.
In most cases, an epithelium is given two names, such as simple squamous, stratified squamous, simple columnar etc.
The first name indicates the number of layers, and the second indicates the shape of the cells at the free surface. Simple
squamous epithelium consists of one layer of flat or scalelike cells that rest on a basement membrane.
Cell layers and cell shapes:
• Simple epithelium, with its single layer of cells, covers surfaces. In the lungs, it facilitates the diffusion of gases;
in the kidney it filters blood; in glands it secrets cellular products and in the intestines it absorbs nutrients.
• Stratified epithelium is found in areas where protection is a major function because it is able to hinder the
selective movement of materials through the epithelium. The multiple layers of cells in stratified epithelium
are well adapted for a protective role. As the outer cells are damaged, they are replaced by cells from deeper
layers; thus, a continuous barrier of epithelial cells is maintained in the tissue.
• Stratified squamous epithelium is found in areas of body where abrasion can occur, such as the skin, mouth,
throat, esophagus, anus and vagina.
Connective tissue: The tissue, which fills the spaces and holds the organs together in animal body is called connective
tissue. It underlies the skin, surrounds nerves and muscles, joins bones and muscles to each other and often stores fat
in its cells.
Features:
1. Originates from the mesodermal layer.
2. The number of cells are relatively low.
3. Huge intracellular spaces are there and the space is filled with matrix.
4. The cells are not arranged in layer and arbitrarily distributed in the matrix.
5. Several types of fibers are there in the matrix.
Functions:
1. It holds other tissues and organs together.
2. It constitutes the supporting framework of the body.
3. It provides the organs to get definite shape and size.
4. It helps in the movement of the body or organs.
5. It provides insulation of the body from the loss of heat.
6. It provides protection against wounding or bacterial invasions.
7. It produces the blood cells.
8. It produces antibody.
Body composition: Body fluid and its compartments
The total body fluid (42 L) is distributed mainly between two compartments:
1
1. The extracellular fluid (14 L): The fluid outside the cells of the body is called extracellular fluid ECF). It is
3
of total body fluid. It is divided into:
i. Interstitial fluid (11 L): The fluid present outside the vascular system and between the cells of the body
is called interstitial fluid.
ii. Plasma (3 L): The plasma is the non-cellular part of the blood. It exchanges substances continuously
with the interstitial fluid through the pores of the capillary membranes.
iii. Transcellular fluid (1-2 L): The fluids within the cavity lined by epithelium which cannot
communicate with other body fluid compartments and don’t participate in the body fluid homeostasis
is called transcellular fluid.
• Fluid in potential spaces: These include –
⸺ Pleural cavity
4
Structure and
Function 1
Book lists:
1. Guyton and Hall Textbook of Medical Physiology
2. Seeley’s Essentials of Anatomy and Physiology
3. Ganong’s Review of Medical Physiology
4. Fundamentals of Anatomy and Physiology
By Martini
1
,1. General Anatomy and General Physiology
Anatomy: Anatomy is the scientific discipline that investigates the body’s structures – for example, the shape and size
of the bones. In addition, anatomy examines the relationship between the structure of a body part and its function.
Thus, the fact that bone cells are surrounded by a hard, mineralized substance enables the bones to provide strength
and support. Understanding the relationship between structure and function makes it easier to understand and
appreciate anatomy.
Physiology: Physiology is the scientific investigation of the processes or functions of living things. The major goals
when studying human physiology are to understand and predict the body’s responses to stimuli and to understand how
the body maintains conditions within a narrow range of values in a constantly changing environment.
Organization of human body: Skeleton, skeletal muscular system
Skeletal system: The organ system of the body, formed mainly by the combination of bones and cartilages to form the
internal framework of the body, to give the definite shape of the body and to protect the inner soft visceral organs from
external pressure and shock is called skeletal system. This system also includes the hard integumentary derivatives like
hairs, furs and nails etc.
Functions:
1. Formation of framework: Bone forms the strong and rigid endoskeleton or framework of the body and support
the body.
2. Protection: The skeleton protects certain vital internal organs such as brain, heart, lungs, liver, spinal cord etc.
3. Connecting area of muscles and ligament: It provides area for attachment of muscles and ligaments.
4. Formation of lever system: Bones forms a system of levers that multiply the forces generated during the
connection of skeletal muscles and transform them into bodily movement.
5. Locomotion: The contraction of skeletal muscles create the movement of the bones. By such the movement
of the muscles of the legs, bipedal locomotion in man is completed.
6. Formation of blood corpuscles: In infants, the blood corpuscles are produced from the red bone marrow of
all bones. In adults, the blood corpuscles are produced in the bone marrow of only the cranium, ribs, sternum,
vertebrae and heads of the humerus and femur. The red bone marrow produces the RBC and hemoglobin.
WBC are also produced from the bone marrow.
7. Defense: The bone marrow also acts as a defensive agent of the body and also takes part in the re-orientation
of the bones.
8. Storage: It serves as a reservoir of calcium, phosphate and other ions and supply them to the blood whenever
necessary.
9. Poison inhibitor: It stores led, arsenic etc. and thus prevents the body from poisonous activity.
10. Destruction: The bone marrow sometimes destroy RBC if necessary.
11. Hearing and breathing: The skeleton helps in many physiological processes. The ear ossicles help in hearing;
the sternum and ribs in breathing.
Tissues, skin and appendages
Tissue: Tissues are groups of cells that have a similar structure and act together to perform a specific function.
Types of animal tissue:
1. Epithelial tissue
2. Connective tissue
3. Muscular tissue and
4. Nervous tissue
They are discussed below:
2
,Epithelial tissue: The tissue which constitutes the outer lining of the body or any internal organ is called epithelial
tissue.
Major features:
1. Mostly composed of cells: Epithelial tissue consists almost entirely of cells, with very little extracellular matrix
between them.
2. Covers body surfaces: Epithelial tissue covers body surfaces and forms glands that are derived
developmentally from body surfaces. The body surfaces include the exterior surface, the lining of the digestive
and respiratory tracts, the heart and blood vessels and the linings of many body cavities.
3. Distinct cell surfaces: Most epithelial tissues have one free or apical surface where cells are exposed and not
attached to other cells. The cells have a lateral surface where cells are attached to other epithelial cells. At the
base of the cells is basal surface attached to a basement membrane. The free surface often lines the lumen of
ducts, vessels and cavities. The basement membrane is a specialized type of extracellular material secreted by
epithelial and connective tissue cells. The basement membrane helps attach the epithelial cells to the underlying
tissues, like the adhesive on Scotch tape. It plays an important role in supporting and guiding cell migration
during tissue repair. The basement membrane is typically porous, which allows substances to move to and
from the epithelial tissue above it. A few epithelial tissues, such as those in lymphatic capillaries and liver
sinusoids, do not have basement membranes, and some epithelial tissues, such as those in some endocrine
glands, do not have a free surface or a basal surface with a basement membrane.
4. Cell and matrix connections: Specialized cell contacts bind adjacent epithelial cells together and to the
extracellular matrix of the basement membrane.
5. Nonvascular: Blood vessels in the underlying connective tissue do not penetrate the basement membrane to
reach the epithelium; thus, all gases and nutrients carried in the blood must reach the epithelium by diffusing
the from blood vessels across the basement membrane. In epithelial tissues with many layers of cells, diffusion
must also occur across the cells, and the most metabolically active cells are close to the basement membrane.
6. Capable of regeneration: Epithelial tissue has the ability to replace damaged cells with new epithelial cells.
Undifferentiated cells (stem cells) continuously divide and produce new cells. In some types of epithelial
tissues, such as those in the skin and digestive tract, new cells continuously replace cells that die.
Functions:
1. Protecting underlying structures: For example, the outer layer of the skin and the epithelium of the oral cavity
protect the underlying structures from abrasion.
2. Acting as a barrier: Epithelium prevents many substances from moving through it. For example, the skin acts
as barrier and reduces water loss from the body. The skin also prevents many toxic molecules and
microorganisms from entering the body.
3. Permitting the passage of substances: Though epithelium acts as a barrier for some substance, it also permits
many other substances to move through it. For example, O2 and CO2 are exchanged between the air and blood
by diffusion through the epithelium in the lungs. Epithelium acts as a filter in the kidney, allowing many
substances to pass from the blood into the urine but retaining other substances, such as blood cells and proteins
in the blood.
4. Secreting substances: Mucus glands, sweat glands and the enzyme-secreting portions of the pancreas are all
composed of epithelial cells that secrete their products onto surfaces or into ducts that carry them to other areas
of the body.
5. Absorbing substances: The plasma membranes of certain epithelial tissues contain carrier proteins, which
regulate the absorption of materials.
Classification:
A. Based on the number of cell layers in each:
1. Simple epithelium: It consists of a single layer of cells, with each cell extending from the basement
membrane to the free surface.
2. Stratified epithelium: It consists of more than one layer of cells, but only the basal layer attaches the
deepest layer to the basement membrane.
3. Pseudostratified columnar epithelium: It is a special type of simple epithelium. The prefix pseudo
means false, so this type of epithelium appears to be stratified but is not. It consists of one layer of
cells, with all the cells attached to the basement membrane. These appear to be two or more layers of
3
, cells because some of the cells are tall and extend to the free surface, whereas others are shorter and
do not extend to the free surface.
B. Based on idealized shapes:
1. Squamous: Squamous cells are flat or scalelike.
2. Cuboidal: They are cube-shaped; about as wide as they are tall.
3. Columnar: Columnar cells tend to be taller than they are wide.
In most cases, an epithelium is given two names, such as simple squamous, stratified squamous, simple columnar etc.
The first name indicates the number of layers, and the second indicates the shape of the cells at the free surface. Simple
squamous epithelium consists of one layer of flat or scalelike cells that rest on a basement membrane.
Cell layers and cell shapes:
• Simple epithelium, with its single layer of cells, covers surfaces. In the lungs, it facilitates the diffusion of gases;
in the kidney it filters blood; in glands it secrets cellular products and in the intestines it absorbs nutrients.
• Stratified epithelium is found in areas where protection is a major function because it is able to hinder the
selective movement of materials through the epithelium. The multiple layers of cells in stratified epithelium
are well adapted for a protective role. As the outer cells are damaged, they are replaced by cells from deeper
layers; thus, a continuous barrier of epithelial cells is maintained in the tissue.
• Stratified squamous epithelium is found in areas of body where abrasion can occur, such as the skin, mouth,
throat, esophagus, anus and vagina.
Connective tissue: The tissue, which fills the spaces and holds the organs together in animal body is called connective
tissue. It underlies the skin, surrounds nerves and muscles, joins bones and muscles to each other and often stores fat
in its cells.
Features:
1. Originates from the mesodermal layer.
2. The number of cells are relatively low.
3. Huge intracellular spaces are there and the space is filled with matrix.
4. The cells are not arranged in layer and arbitrarily distributed in the matrix.
5. Several types of fibers are there in the matrix.
Functions:
1. It holds other tissues and organs together.
2. It constitutes the supporting framework of the body.
3. It provides the organs to get definite shape and size.
4. It helps in the movement of the body or organs.
5. It provides insulation of the body from the loss of heat.
6. It provides protection against wounding or bacterial invasions.
7. It produces the blood cells.
8. It produces antibody.
Body composition: Body fluid and its compartments
The total body fluid (42 L) is distributed mainly between two compartments:
1
1. The extracellular fluid (14 L): The fluid outside the cells of the body is called extracellular fluid ECF). It is
3
of total body fluid. It is divided into:
i. Interstitial fluid (11 L): The fluid present outside the vascular system and between the cells of the body
is called interstitial fluid.
ii. Plasma (3 L): The plasma is the non-cellular part of the blood. It exchanges substances continuously
with the interstitial fluid through the pores of the capillary membranes.
iii. Transcellular fluid (1-2 L): The fluids within the cavity lined by epithelium which cannot
communicate with other body fluid compartments and don’t participate in the body fluid homeostasis
is called transcellular fluid.
• Fluid in potential spaces: These include –
⸺ Pleural cavity
4
