TISSUE LEVEL OF ORGANIZATION – Human Anatomy and Physiology B. Pharma 1st Semester

Human Anatomy and


Human Anatomy:
Deals with the structure of the human body and the relationship among the

Deals with body functions


Helps us to learn about the structure and functions of human
body and the inter relationship 

Parameters of normal body health and factors affecting
normal body processes can be known

Forms the basis for proper diagnosis of a disease and its
effective treatment

Anatomical and Physiological concepts help in efficient surgeries
and understanding the pathology of diseases  

Basis for advanced scientific studies and serves as a
gateway to get into health related careers

Helps in successful maintenance of community and individual

Subspecialties of Anatomy

Embryology •
First 8 weeks of development

Developmental Biology
From fertilization of an egg to death

Cell Biology •
Cellular structure and functions

Histology •
Microscopic structure of tissues

Surface anatomy •
Surface markings of the body

Gross anatomy
Structures – Without the use of microscope

Systemic anatomy •
Structures – Specific systems

Regional anatomy •
Specific regions of the body

Radiographic anatomy
Structures – Visualized with X – rays

Pathological anatomy
Structural changes with disease

Neurophysiology •
Functional properties of nerve cells

Endocrinology •
Hormones and their control

Physiology •
Functions of heart and blood vessels

Immunology •
Defense against disease causing organisms

Physiology •
Functions of air passageways and lungs

Renal Physiology •
Functions of kidneys

Exercise Physiology •
Muscular activities – Changes

Pathophysiology •
Functional changes – Disease and aging

Levels of Organization

organisms are made up of four levels of organization: cells, tissues, organs,
and organ systems. Order the levels of organization for living organisms

Key Points

Cells are
the most basic unit of life at the smallest level of organization.

Cells can
be prokaryotic (without nucleus) or eukaroyotic (with nucleus).

The four
categories of tissues are connective, muscles, epithelial, and nervous tissues.

Organs are
made of different types of tissues and perform complex functions. They can be
hollow or solid.

systems are groups of organs that perform similar functions or perform
functions together.

physiological functions are carried out by multiple organ systems working in

Key Terms

Cell: The
smallest unit of life capable of independent reproduction. Generally contains
nucleic acid, cytoplasm, a cell membrane, and many other proteins and

Organ: A
structure made of different tissues that work together to perform physiological

system: A group of organs and tissues that work together to perform specific functions.

Tissues: A
group of similar cells with the same origin that work together to perform the
same function.


Using the
circulatory system as an example, a cell in this system is a red blood cell,
the heart’s cardiac muscle is a tissue, an organ is the heart itself, and the
organ system is the circulatory system.

An organism
is made up of four levels of organization: cells, tissues, organs, and organ
systems. These levels reduce complex anatomical structures into groups; this
organization makes the components easier to understand.

Level 1:

The first and most basic level of organization is the cellular level. A
cell is the basic unit of life and the smallest unit capable of reproduction.
While cells vary greatly in their structure and function based on the type of
organism, all cells have a few things in common. Cells are made up of organic
molecules, contain nucleic acids (such as DNA and RNA), are filled with fluid
called cytoplasm, and have a membrane made out of lipids. Cells also contain
many structures within the cytoplasm called organelles, which perform various
cellular functions.

Cells may be prokaryotic (without a nucleus) in bacteria and archaea
(single-celled organisms), or eukaryotic (with nucleus-enclosing DNA) in
plants, animals, protists, and fungi. In humans, most cells combine to form
tissues, but some cells are found independent of solid tissues and have their
own functions. A red blood cell found circulating in the bloodstream carrying
oxygen throughout the human body is an example of an independent cell.

Level 2:

Tissues are a group of similar cells of the same origin that carry out a
specific function together. Humans have four different types of basic tissues.
Connective tissues such as bone tissue are made up of fibrous cells and give
shape and structure to organs. Muscle tissue is made up of cells that can
contract together and allow animals to move. Epithelial tissues make up the
outer layers of organs, such as the skin or the outer layer of the stomach.
Nervous tissue is made of specialized cells that transmit information through
electrochemical impulses, such as the tissue of nerves, the spinal cord, and
the brain.

Level 3:

An organ is a structure made up of different tissues that perform
specific bodily functions. Most organs contain tissues such as parenchyma (used
to perform the organ functions), stroma (connective tissue specific to organs)
and epithelial. Organs may be solid or hollow, and vary considerably in size
and complexity. The heart, lungs, and brain are all examples of organs.

Level 4:
Organ Systems

An organ system is a collection of organs that that work together to
perform a similar function. There are eleven different organ systems in the
human body, each with its own specific functions. One example is digestive
system, which is made up of many organs that work together to digest and absorb
nutrients from food. While most organ systems control a few specific
physiological processes, some processes are more complex and require multiple
organ systems to work together. For example, blood pressure is controlled by a
combination of the renal system (kidneys), the circulatory system, and the
nervous system.

of Organization in Animals
: An organism contains organ systems made up of organs that consist of
tissues, which are in turn made up of cells.

5. Different
Basic Terminologies Used in Anatomy & Physiology


directional terms include anterior and posterior, dorsal and ventral, and
lateral and medial.


how axes give direction, detail, and location when describing a region of the


terms describe the different parts of the body by the structures and functions
of a specific region. The most basic regional terms are the axial and
appendicular regions.

Axes use
directional terms to describe the location and orientation of a specific

directional term lateral is used to describe structures divided by a
left-to-right axis.


ventral: On the front side of the human
body or the corresponding surface of an animal, usually the lower surface.

posterior: Nearer the caudal end of the body
in quadrupeds or the dorsal end in bipeds.

axis: A line between two points that is
used to give direction to an anatomical region.

Terms in Anatomy

terms describe anatomy by dividing the parts of the body into different regions
that contain structures that are involved in similar functions. Two primary
terms are used to describe the main regions of the body:

Axial Region 
up the main axis of the human body and includes the head, neck, chest, and

Appendicular Region 
makes up the parts of the human body that connect to the axial region.
This includes the limbs and appendages.

These are
the two basic categories of regional terms; however, many other terms are used
to describe smaller regions within the axial and appendicular regions. For
example, the brachial region consists of the arm as a part of the appendicular
region, while the abdominal region consists of the abdomen as a smaller part of
the axial region.

abdominal region is subdivided into even smaller regions based on different
functions of groups of organs and tissues in that region. If a person is experiencing
pain in one part of the abdominal region, then the smaller regional divisions
can help determine the organs involved in the problem to better treat symptoms.

Describe Relative Positions

method for describing region An axis uses a straight line between two parts of
the body to describe a region of the body with linear direction. For example,
blood can be said to flow
in a proximal or distal direction through a region marked by that axis. The X,
Y, and Z axes of the Cartesian coordinate system are used describe the specific
location of an axis in standard anatomical position.

Many types
of axes can give regional direction. Any pair of corresponding directional
terms can be combined to form an axis (such as proximal-distal for an

Dorsoventral axis (DV axis) 
is formed by the connection of the dorsal and ventral points of a
region. The region between the belly (ventral) and back (dorsal) is often
described by a DV axis.

Anterioposterior axis (AP axis) 
is the axis formed by the connection of the
anterior (top) and posterior (bottom) ends of a region. The AP axis of a region
is by definition perpendicular to the DV axis and vice-versa.

Left-to-right axis 
is the axis connecting the left and right hand sides of a region. It is
used to describe the lateral sides of a region, which in humans are often
symmetrical around the center of the body. It is perpendicular to both the DV
and AP axes.

Directional AP Axes in Three Body Segments of a Horse
: Axis (A) (in red) shows the AP
axis of the tail, (B) shows the AP axis of the neck, and (C) shows the AP axis
of the head.

Axes give
more clarity and detail for describing the location of an anatomical region.
They are commonly used in both zoology and human anatomy, and can be paired
with body planes to give even more detail to anatomical direction, region, and

When an
organism is in its standard anatomical position, positional descriptive terms
are used to indicate regions and features

In standard
anatomical position, the limbs are placed similarly to the supine position
imposed on cadavers during autopsy.

anatomical position of the skull is the Frankfurt plane. In this position, the
lower margins of the orbitals (eye sockets), the lower margin of the orbits,
and the upper margins of the ear canals (poria) lie in the same horizontal

Because animals can change orientation with respect to their environments
and appendages can change position with respect to the body, positional
descriptive terms refer to the organism only in its standard anatomical
position to prevent confusion.


 appendage: A
limb of the body.

 supine: Lying on its back,

 anatomical position: The
standard position in which the body is standing with feet together, arms to the
side, and head, eyes, and palms facing forward.

The Need
for Standardization

Standard anatomical position is the body orientation used when describing
an organism’s anatomy. Standardization is necessary to avoid confusion since
most organisms can take on many different positions that may change the
relative placement of organs. All descriptions refer to the organism in its
standard anatomical position, even when the organism’s appendages are in
another position. Thus, the standard anatomical position provides a “gold
standard” when comparing the anatomy of different members of the same species.

location in the anatomical position:
Many terms are used
to describe relative location on the body. Cranial refers to features closer to
the head, while caudal refers to features closer to the feet. The front of the
body is referred to as anterior or ventral, while the back is referred to as
posterior or dorsal. Proximal and distal describe relative position on the
limbs. Proximal refers to a feature that is closer to the torso, while distal
refers to a feature that is closer to the fingers/toes. Medial and lateral
refer to position relative to the midline, which is a vertical line drawn
through the center of the forehead, down through the belly button to the floor.
Medial indicates a feature is closer to this line, while lateral indicates
features further from this line.

Anatomical Position in Humans

standard anatomical position is agreed upon by the international medical
community. In this position, a person is standing upright with the lower limbs
together or slightly apart, feet flat on the floor and facing forward, upper
limbs at the sides with the palms facing forward and thumbs pointing away from
the body, and head and eyes directed straight ahead. In addition, the arms are
usually placed slightly apart from the body so that the hands do not touch the
sides. The positions of the limbs, particularly the arms, have important
implications for directional terms in those appendages.

The basis
for the standard anatomical position in humans comes from the supine position
used for examining human cadavers during autopsies. Dissection of cadavers was
one of the primary ways humans learned about anatomy throughout history, which
has tremendously influenced the ways by which anatomical knowledge has
developed into the scientific field of today.

In humans,
the standard anatomical position of the skull is called the Frankfurt plane. In
this position, the orbitales (eye sockets), lower margins of the orbits, and
the poria (ear canal upper margins) all lie in the same horizontal plane. This
orientation represents the position of the skull if the subject were standing
upright and looking straight ahead.

It is
important to note that all anatomical descriptions are based on the standard
anatomical position unless otherwise stated.


Positional terms
give precise descriptions of anatomical relationships and allow for consistency
when referencing anatomical positions.

Key Points

of directional terms include: a) superior (head) and inferior (caudal), b)
anterior and posterior, c) lateral and medial, d) deep and superficial, e)
proximal and distal, and f) dorsal and ventral.

terms provide comparison of anatomical position by comparing the locations of
different structures in the body.

Key Terms

Directional terms: Directional terms are words used to describe
the location of an anatomical structure by comparing its position to other
structures within the body or within the orientation of the body itself.

Anatomy with Language

terms provide precise descriptions of a structure’s location. They allow a
description of anatomical position by comparing location relative to other
structures or within the rest of the body. Standard anatomical terms for
direction include:

and inferior (cranial and caudal) are used when referring to parts of the body
which are toward an end of the body. Superior structures are toward the head
(cranial) while inferior (caudal) structures are toward the feet. Examples
include the superior and inferior vena cava, which carry deoxygenated blood away
from the head (superior) and from the lower body (inferior) to the heart.

and posterior are sometimes used in place of superior and inferior,
respectively. These words are used more often for animal anatomy and rarely and
only with very specific meaning in human anatomy. Anterior refers to the side
of the structure facing up in the standard anatomical position while posterior
refers to the bottom side. For example, the pituitary gland has an anterior and
posterior side, each of which secretes different types of hormones.

Dorsal and
ventral are sometimes used in place of anterior and posterior, respectively.
Dorsal means the back side or upper side, while ventral means the frontal or
lower side. These are mostly used with animal anatomy, but can be used in human
anatomy as long as they are describing the side of an appendage. One example is
the dorsal fin in fish, found on the upper side of the fish’s body.

Lateral is
used to describe anything closer to the sides of the body (toward the arms, in
the standard anatomical position), whilemedial is used to describe anything
toward the middle of the body. In general, many structures of the human body
are bilateral and symmetrical with the middle of the body, such as the lungs or
the arms.

Deep refers
to structures closer to the interior center of the body. For example, bones in
an appendage are located deeper than the muscles. Superficial is used to
describe structures that are closer to the exterior surface of the body. For
example, the outer layers of skin are superficial to deeper layers of skin.

and Distal describe one point relative to another. Proximal refers to a point
closer to the reference point while distal refers to a point farther away. When
describing appendages, the proximal end of the appendage connects the appendage
to the body, while the distal end is away from the body.

Body Planes:-

There are
three basic reference planes used in anatomy: the sagittal plane, the coronal
plane, and the transverse plane.

Key Points

A coronal
or frontal plane divides the body into dorsal and ventral (back and front, or
posterior and anterior) portions.

transverse plane, also known as an axial plane or cross-section, divides the
body into cranial and caudal (head and tail) portions.

A sagittal
plane divides the body into sinister and dexter (left and right) portions.

Body planes
have several uses within the anatomy field, including in medical imaging, descriptions
of body motion, and embryology.

Key Terms

Coronal plane: Any vertical plane that divides the body into
anterior and posterior (belly and back) sections.

Transverse plane: Any plane that divides the body into superior
and inferior parts, roughly perpendicular to the spine.

Sagittal plane: Any imaginary plane parallel to the median

What Are Body Planes?

Body planes
are hypothetical geometric planes used to divide the body into sections. They
are commonly used in both human and zoological anatomy to describe the location
or direction of bodily structures. Reference planes are the standard planes
used in anatomical terminology and include:

sagittal plane (lateral or Y-Z plane) divides the body into sinister and dexter
(left and right) sides. The midsagittal (median) plane is in the midline
through the center of the body, and all other sagittal planes are parallel to

The coronal
plane (frontal or Y-X plane) divides the body into dorsal and ventral (back and
front) portions. It also separates the anterior and posterior portions.

transverse plane (axial or X-Z plane) divides the body into superior and
inferior (head and tail) portions. It is typically a horizontal plane through
the center of the body and is parallel to the ground.

While these
are the major reference planes of the body, other planes are commonly used in
relation to these three. A longitudinal plane is any plane perpendicular to the
transverse plane, while parasaggital planes are parallel to the saggital plane.

The coronal
plane, the sagittal plane, and the parasaggital planes are examples of


Planes in a Human: There are three basic planes in zoological anatomy:
sagittal, coronal, and transverse. A human in the anatomical position, can be described
using a coordinate system with the Z-axis going from front to back, the X-axis
going from left to right, and the Y-axis going from up to down.

Applications of Body Planes

imaging techniques such as sonography, CT scans, MRI scans, or PET scans are
one of the primary applications of body planes. By imaging a patient in
standard anatomical position, a radiologist can build an X-Y-Z axis around the
patient to apply body planes to the images. The planes can then be used to
identify and locate the positions of the patient’s internal organs. Individual
organs can also be divided by planes to help identify smaller structures within
that organ.

Body planes
are used to describe anatomical motion in the X-Y-Z coordinate system that the
body moves through. An anatomist could model a limb’s range of motion by
measuring which planes the limb can move through and how far it is able to

change during embryological development is also described and measured with
body planes. For example, during human embryonic development the coronal plane
is horizontal, but becomes vertical as the embryo develops into a fetus. In
comparative embryology, body planes provide a basis for comparing the ways in
which different types of organisms develop anatomically within the womb.



The dorsal
cavity contains the primary organs of the nervous system, including the brain
and spinal cord.

diaphragm is a sheet of muscle that separates the thoracic cavity from the
abdominal cavity.

membrane tissues surround the body cavities, such as the meninges of the dorsal
cavity and the mesothelium of the ventral cavity.

mesothelium consists of the pleura of the lungs, the pericardium of the heart,
and the peritoneum of the abdominopelvic cavity.


: The ventral
body chamber that contains the abdominal cavity (primarily digestive system)
and the pelvic cavity (primarily reproductive system).

: The cavity
in the back of the body that contains the cranial and vertebral cavities, which
house the brain and spinal cord respectively.

: The ventral
body chamber that contains the pericardial cavity (the heart) and the pleural
cavity (the lungs).

By the
broadest definition, a body cavity is any fluid-filled space in a multicellular
organism. However, the term usually refers to the space where internal organs
develop, located between the skin and the outer lining of the gut cavity.”The
human body cavity,” normally refers to the ventral body cavity because it is by
far the largest one in volume. Blood vessels are not considered cavities but
may be held within cavities. Most cavities provide room for the organs to
adjust to changes in the organism’s position. They usually contains protective
membranes and sometimes bones that protect the organs.

terminology for body cavities
: Humans have multiple body cavities, including the cranial cavity, the
vertebral cavity, the thoracic cavity (containing the pericardial cavity and
the pleural cavity), the abdominal cavity, and the pelvic cavity. In mammals,
the diaphragm separates the thoracic cavity from the abdominal cavity.


The dorsal
cavity is a continuous cavity located on the dorsal side of the body. It houses
the organs of the upper central nervous system, including the brain and the
spinal cord. The meninges is a multi-layered membrane within the dorsal cavity
that envelops and protects the brain and spinal cord.


The cranial
cavity is the anterior portion of the dorsal cavity consisting of the space
inside the skull. This cavity contains the brain, the meninges of the brain,
and cerebrospinal fluid.


vertebral cavity is the posterior portion of the dorsal cavity and contains the
structures within the vertebral column. These include the spinal cord, the
meninges of the spinal cord, and the fluid-filled spaces between them. This is
the most narrow of all body cavities, sometimes described as threadlike.


The ventral
cavity, the interior space in the front of the body, contains many different
organ systems. The organs within the ventral cavity are also called viscera.
The ventral cavity has anterior and posterior portions divided by the
diaphragm, a sheet of skeletal muscle found beneath the lungs.


thoracic cavity is the anterior ventral body cavity found within the rib cage
in the torso. It houses the primary organs of the cardiovascular and
respiratory systems, such as the heart and lungs, but also includes organs from
other systems, such as the esophagus and the thymus gland. The thoracic cavity
is lined by two types of mesothelium, a type of membrane tissue that lines the
ventral cavity: the pleura lining of the lungs, and the pericadium lining of
the heart.


abdominoplevic cavity is the posterior ventral body cavity found beneath the
thoracic cavity and diaphragm. It is generally divided into the abdominal and
pelvic cavities. The abdominal cavity is not contained within bone and houses
many organs of the digestive and renal systems, as well as some organs of the
endocrine system, such as the adrenal glands. The pelvic cavity is contained
within the pelvis and houses the bladder and reproductive system. The
abdominopelvic cavity is lined by a type of mesothelium called the peritoneum.

6. Summary

Anatomy and
Study of Structure & functions of human body

Levels of
 Atomic level to organismal level

Each of the
body systems has several functions and these are interconnected

systems work together to maintain homeostasis

terms, body planes and cavities:
Help to describe the body structure

and directional terms:
Useful to differentiate body landmarks

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