Anatomical Orientation

Introduction to anatomy, its wording, terms, regions, planes, cavities, and placements.  All understandings of anatomy and physiology come from the basic knowledge of anatomical orientation.

Etymology 

Latin was chosen as the universal language of science.  Studying anatomy means learning a new language at the same time.  At times Latin is used for full phases, or just roots, prefixes, or suffixes.  At other times some elements of the Greek language will be used without any set rules for its uses.

Root Words, Prefixes, And Suffixes

Anatomical Positioning

Anatomical position is a fundamental concept in human anatomy and is used as a reference point for describing the location of various anatomical structures. It is a standardized position that all anatomical descriptions are based upon. The anatomical position is defined as a standing posture, with the feet shoulder-width apart and parallel to each other, the arms at the sides of the body, and the palms facing forward. The individual's head is also held erect and facing forward.

The individual's body is divided into two main regions, the axial region and the appendicular region. The axial region includes the head, neck, and trunk, while the appendicular region includes the upper and lower limbs.

The direction of movement and orientation of body parts are described in relation to three primary anatomical planes: the sagittal plane, the frontal plane, and the transverse plane. The sagittal plane divides the body into right and left portions. The frontal plane divides the body into front and back portions, and the transverse plane divides the body into upper and lower portions.

When describing the location of anatomical structures, specific anatomical terms are used. For example, the terms "anterior" and "posterior" are used to describe the front and back of the body, respectively. "Superior" and "inferior" refer to the top and bottom of the body, while "medial" and "lateral" describe structures closer to or further from the midline of the body.

Directional Terms

Anatomical directional terms are used to describe the location and orientation of various structures in the body. These terms provide a standardized language for communicating anatomical information and are essential for accurate communication between healthcare professionals.

·         Superior/Inferior: Superior refers to a structure that is further away from normal, or ground level, or upper part of the body, while inferior refers to a structure that is closer to the ground or lower part of the body. For example, in humans the head is superior to the neck, and the feet are inferior to the knees.

o   Cranial/Caudal: Cranial refers to moving closer to towards the head, while caudal is moving away from the head or towards bottom of the body.  In humans, cranial and superior are synonymous while caudal and inferior are the same in bipedal organisms.  In quadrupeds, cranial is towards head, superior is towards back, caudal is towards posterior, and inferior is towards feet.

·         Anterior/Posterior: Anterior refers to a structure that is closer to the front of the body, while posterior refers to a structure that is closer to the back of the body. For example, the nose is anterior to the ears, and the spine is posterior to the heart.

o   Dorsal/Ventral: Dorsal refers to the vertebral side of the body, while ventral refers to the belly side of the body.  In humans, dorsal and posterior are the same since the back of the body is the same side as the vertebrae are in the same location.  While ventral and anterior are the same since the front of the body is also the belly side in bipedal organisms.

·         Medial/Lateral: Medial refers to a structure that is closer to the midline of the body, while lateral refers to a structure that is further away from the midline of the body.

·         Proximal/Distal: Proximal refers to a structure that is closer to the trunk of the body or the point of origin, while distal refers to a structure that is further away from the trunk of the body or the point of origin. For example, the elbow is proximal to the wrist, and the fingers are distal to the wrist.

·         Superficial/Deep: Superficial refers to a structure that is closer to the surface of the body, while deep refers to a structure that is further away from the surface of the body. For example, the skin is superficial to the muscles, and the bones are deep to the skin.

·         Ipsilateral/Contralateral: Ipsilateral refers to structures that are on the same side of the body, while contralateral refers to structures that are on opposite sides of the body. For example, the right arm and leg are ipsilateral, while the right arm and left leg are contralateral.

Regions

The human body can be divided into various regions that help in understanding the structure and function of different parts. These regions can be further divided into subregions and parts. Here is a detailed explanation of all the regions of the human body including all subregions and parts.

·         Head and neck region: this region comprises the head and neck. It can be further divided into the following subregions:

o    The cranial region comprises the skull and brain. The skull is made up of different bones that protect the brain. The brain is the control center of the body, responsible for processing and coordinating sensory input and motor output.

o    The facial region comprises the face and its various features. It includes the eyes, ears, nose, mouth, and cheeks. These features are important for sensory perception, communication, and expression.

o    The cervical region comprises the neck, which connects the head to the rest of the body. It contains important structures such as the cervical vertebrae, trachea, and thyroid gland.

·         Trunk: includes thoracic, abdominal, and pelvic regions

o    The thoracic region comprises the chest and its contents. It can be further divided into the following subregions:

§  The thoracic cavity is a space within the chest that contains the heart, lungs, and major blood vessels. The heart is responsible for pumping blood to the rest of the body, while the lungs are responsible for oxygenating blood.
Sternal region:  this region creates an anterior portion of the chest’s wall.

§  The mammary region comprises the breasts and areola. The breasts are important for lactation.

§  The scapular region makes up a small portion of the posterior thoracic wall around the shoulder blade and the glenoid cavity.

o    The abdominal region comprises the abdomen and its contents. It can be further divided into the following subregions:

§  The abdominal cavity is a space within the abdomen that contains the digestive organs such as the stomach, small intestine, and large intestine. It also contains the liver, pancreas, and spleen.

§  The umbilicus is central of the anterior abdominal region, defined by the location where the umbilical cord was attached

§  The lumbar region is location in the lower posterior abdominal wall, where the lumbar vertebra are located.

o    The pelvic cavity is a space within the pelvis that contains the reproductive organs such as the uterus, ovaries, and vagina (in females) or the prostate gland, testes, and penis (in males). It also contains the bladder and rectum.

·         Upper limb region: this region comprises the upper limbs or arms. It can be further divided into the following parts:

o    The acromial (shoulder) is the joint that connects the arm to the trunk of the body. It is made up of the clavicle and scapula.

o    The axillary is where the axilla (arm pit) branches from the trunk.

o    The brachial (upper arm) is the upper part of the limb that extends from the shoulder to the elbow. It is made up of the humerus bone.

o    The antebrachial (forearm) is the lower part of the limb that extends from the elbow to the wrist. It is made up of the radius and ulna bones.

o    The carpal (wrist) is where the forearm meets the hand, including small short bones called carpals that allow movement of the hand.

o    The manus (hand) is the distal part of the limb that contains the wrist, palm, and fingers. It is made up of various bones such as the carpals, metacarpals, and phalanges.

·         Lower limb region: this region comprises the lower limbs or legs. It can be further divided into the following parts:

o    The coxal (hip) is the joint that connects the leg to the trunk of the body. It is made up of the pelvis and femur bone.

o    The femoral (thigh) is the upper part of the limb that extends from the hip to the knee. It is made up of the femur bone.

o    The leg is the lower part of the limb that extends from the knee to the ankle. It is made up of the tibia and fibula bones.

o    The tarsal (ankle) is where the leg meets the foot, including short bones called tarsals that allow movement of the foot.

o    The pedal (foot) is the distal part of the limb that contains the ankle, sole, and toes. It is made up of various bones such as the tarsals, metatarsals, and phalanges.

Cavities

The human body contains several cavities that house and protect internal organs. These cavities are divided into two main categories: dorsal cavities and ventral cavities.

·         The dorsal cavities are located on the posterior (back) side of the body and are protected by bone. They include the cranial cavity and the vertebral cavity.

o   The cranial cavity is the space within the skull that contains the brain. It is protected by the bones of the skull and is lined with three layers of protective membranes called meninges.

o   The vertebral cavity is the space within the vertebral column that contains the spinal cord. It is protected by the vertebrae and is also lined with meninges.

·         The ventral cavities are located on the anterior (front) side of the body and are not protected by bone. They are divided into two main cavities: the thoracic cavity and the abdominopelvic cavity.

o   The thoracic cavity is located superior (above) to the diaphragm and is surrounded by the rib cage. It contains the lungs, heart, and major blood vessels. The thoracic cavity is divided into two sub cavities: the pleural cavities and the mediastinum.

§  The pleural cavities are located on either side of the mediastinum and contain the lungs. They are lined with a serous membrane called the pleura.

§  The mediastinum is located between the two pleural cavities and contains the heart within the pericardial cavity, major blood vessels, thymus gland, and other structures. It is divided into three compartments: the superior, middle, and inferior mediastinum.

§  The pericardial cavity contains the heart and the pericardium which is a serous membrane that covers the heart.

o   The abdominopelvic cavity is located inferior (below) to the diaphragm and is not surrounded by bone. It contains the digestive organs, urinary organs, reproductive organs, and other structures. The abdominopelvic cavity is divided into two sub cavities: the abdominal cavity and the pelvic cavity.

§  The abdominal cavity is located superior to the pelvic cavity and contains the digestive organs, such as the stomach, liver, pancreas, spleen, and intestines. It is lined with a serous membrane called the peritoneum.

§  The pelvic cavity is located inferior to the abdominal cavity and contains the urinary and reproductive organs, such as the bladder, uterus, and ovaries. It is also lined with the peritoneum.

Abdominopelvic Divisions

The abdominopelvic cavity is the largest cavity in the human body and is divided into four quadrants and nine regions. These divisions are essential in clinical settings, such as during physical examinations, diagnostic imaging, and surgical procedures.

The four quadrants of the abdominopelvic cavity are formed by drawing an imaginary vertical line and a horizontal line through the umbilicus, which is the belly button.

·         The right upper quadrant (RUQ) is located superior and to the right of the umbilicus, and it contains the liver, gallbladder, and parts of the stomach and small intestine.

·         The left upper quadrant (LUQ) is located superior and to the left of the umbilicus, and it contains the spleen, pancreas, and parts of the stomach and small intestine.

·         The right lower quadrant (RLQ) is located inferior and to the right of the umbilicus, and it contains the appendix, cecum, and parts of the small intestine and colon.

·         The left lower quadrant (LLQ) is located inferior and to the left of the umbilicus, and it contains the sigmoid colon, parts of the small intestine and colon, and the left ovary and fallopian tube in females.

The nine regions of the abdominopelvic cavity are more precise and allow for a more accurate description of the location of internal organs. These regions are defined by drawing four imaginary planes through the abdomen. The planes include two horizontal planes, the subcostal plane and the intertubercular plane, and two vertical planes, the midclavicular plane and the median plane.

Starting from the top of the abdominopelvic cavity, the nine regions are as follows:

·         The right hypochondriac region is located superior and to the right of the umbilical region; contains the liver, gallbladder, and right kidney.

·         The epigastric region is located superior to the umbilical region; contains the stomach, pancreas, and part of the liver.

·         The left hypochondriac region is located superior and to the left of the umbilical region; contains the spleen and left kidney.

·         The right lumbar region is located lateral and to the right of the umbilical region; contains the ascending colon, liver, and right kidney.

·         The umbilical region is located around the umbilicus; contains the transverse colon, small intestine, and part of the aorta.

·         The left lumbar region is located lateral and to the left of the umbilical region; contains the descending colon, left kidney, and part of the spleen.

·         The right iliac (inguinal) region is located inferior and to the right of the umbilical region; contains the cecum, appendix, and right ovary and fallopian tube in females.

·         The hypogastric (pubic) region is located inferior to the umbilical region; contains the bladder, uterus, and prostate gland.

·         The left iliac (inguinal) region is located inferior and to the left of the umbilical region; contains the sigmoid colon and left ovary and fallopian tube in females.

Planes

The planes of the body are imaginary lines used to divide the body into different sections or parts for anatomical study and analysis. There are several planes of the body, including the midsagittal plane, parasagittal plane, frontal plane, facial plane, transverse plane, and oblique plane.

·         The midsagittal plane is a vertical plane that divides the body into two equal halves, with one half on the right and the other half on the left. This plane runs through the midline of the body, dividing it into two symmetrical halves. The midsagittal plane is also known as the median plane and is commonly used in medical imaging and surgical procedures.

·         The parasagittal plane is a vertical plane that runs parallel to the midsagittal plane, dividing the body into unequal right and left sections. This plane is useful for studying structures that are located more towards one side of the body.

·         The frontal plane, also known as the coronal plane, is a vertical plane that divides the body into anterior (front) and posterior (back) sections. This plane runs perpendicular to the midsagittal plane, dividing the body into a front and a back portion. The frontal plane is commonly used in medical imaging and surgical procedures to view the front and back sections of the body.

·         The facial plane is a plane that passes through the face and head, dividing the body into anterior and posterior sections. This plane is useful for studying facial and cranial structures.

·         The transverse plane, also known as the horizontal plane or cross-sectional plane, is a plane that divides the body into cranial (upper) and caudal (lower) sections. This plane runs parallel to the ground and is perpendicular to both the sagittal and frontal planes. The transverse plane is commonly used in medical imaging and surgical procedures to view internal organs and structures.

·         The oblique plane is a plane that passes through the body at an angle other than the previously mentioned planes. This plane is useful for studying structures that are not easily visible with the other planes.

Organ Systems

The human body is composed of various organ systems that work together to maintain homeostasis and ensure the proper functioning of the body. There are eleven organ systems in the human body, each with a specific set of functions. In this explanation, we will discuss each of these organ systems in detail.

·         The integumentary system is composed of the skin, hair, nails, and sweat glands. The primary function of this system is to protect the body from external damage, regulate body temperature, and provide sensory information.

·         The skeletal system is made up of bones, cartilage, and ligaments. The skeletal system provides support for the body, protects internal organs, and enables movement.

·         The muscular system is made up of muscles and tendons. This system enables movement, maintains posture, and generates heat.

·         The nervous system is made up of the brain, spinal cord, and nerves. This system regulates and coordinates body functions, processes sensory information, and enables communication between different parts of the body.

·         The endocrine system is made up of glands that secrete hormones. These hormones regulate body functions, such as growth and development, metabolism, and reproductive processes.

·         The cardiovascular system is composed of the heart, blood vessels, and blood. The primary function of this system is to transport nutrients, oxygen, and hormones throughout the body.

·         The lymphatic system is made up of lymph nodes, lymphatic vessels, and lymphoid organs. This system helps to maintain fluid balance in the body, fight infection, and remove waste.

·         The respiratory system is made up of the lungs, trachea, and bronchial tubes. The primary function of this system is to take in oxygen and release carbon dioxide.

·         The digestive system is made up of the mouth, esophagus, stomach, small intestine, large intestine, and accessory organs such as the liver and pancreas. The primary function of this system is to break down food into nutrients and eliminate waste.

·         The urinary system is composed of the kidneys, ureters, bladder, and urethra. The primary function of this system is to filter waste products from the blood and eliminate them from the body.

·         The reproductive system is different in males and females but the overall function is the same. It is responsible for producing gametes (sperm and egg cells), and for the continuation of the species through reproduction.

The eleven organ systems of the human body work together to maintain homeostasis and ensure the proper functioning of the body. Each system has a specific set of functions that are essential for survival.

Overview

The study of human anatomy involves understanding the body's regions, cavities, planes, and organ systems. Anatomical orientation is based on the anatomical position, which is a standardized reference point for describing the location of various structures. The body is divided into axial and appendicular regions, and specific anatomical terms are used to describe the location and orientation of body parts.

Latin and Greek roots, prefixes, and suffixes form the basis of anatomical language, providing a universal way for scientists to communicate about the human body. The body is divided into various regions, such as the head, neck, trunk, upper limbs, and lower limbs, which are further divided into subregions and parts.

The body contains several cavities, including dorsal and ventral cavities, which house and protect internal organs. The abdominopelvic cavity is the largest cavity and is divided into four quadrants and nine regions for precise description of organ locations.

The planes of the body are imaginary lines used to divide the body into different sections for anatomical study. These include the midsagittal, parasagittal, frontal, facial, transverse, and oblique planes.

The human body consists of eleven organ systems, including the integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, and reproductive systems. Each system has specific functions and works together to maintain homeostasis and ensure the proper functioning of the body. Understanding these aspects of human anatomy is essential for medical professionals and anyone interested in the structure and function of the human body.