Basic concepts of structural organization of human body

Basic concepts of structural organization of human body

At the end of this session, a student should be able to;

• Define the terms anatomy, cytology and histology
• Explain approaches of studying anatomy
• Explain anatomical positions
• Explain body regions
• Explain anatomical planes
• Explain body cavities
• Explain relationship and comparison of different parts of the body
• Explain different types of body movements

Describe structural organization levels of human body

DEFINITION OF THE TERM ANATOMY, CYTOLOGY AND HISTOLOGY

ANATOMY

It is a Greek word ( Ana-Tome): meaning cutting up.

Anatomy – the study of the structure of body parts and their relationships to one another.

• Cytology – study of the cell

Histology – study of tissues

APPROACHES OF STUDYING ANATOMY

SUBDIVISION

Gross (Macroscopic) Anatomy

Microscopic Anatomy

Developmental Anatomy

Specialized Branches of Anatomy

Gross (Macroscopic Anatomy

• Systemic – gross anatomy of the body studied by system

Surface – study of internal structures as they relate to the overlying skin

Microscopic Anatomy

• Cytology – study of the cell

Histology – study of tissues

Developmental Anatomy

 Embryology – study of developmental changes of the body before birth(embryogenesis and subsequent organogenesis)

Specialized Branches of Anatomy

•  Pathological anatomy – study of structural changes caused by disease
• Radiographic anatomy – study of internal structures visualized by X ray

Molecular biology – study of anatomical structures at a sub-cellular level

DEFINITION OF TERMS USED TO DESCRIBE POSITIONS/LOCATION, LATERALITY AND BODY MOVEMENTS

Anatomical Position

The anatomical position is a standardized method of observing or imaging the body that allows precise and consistent anatomical references.

• When in the anatomical position, the subject stands (Fig 1.5)
• Standing upright
• Facing the observer, head level
• Eyes facing forward
• Feet flat on the floor
• Arms at the sides

Palms turned forward (ventral)

Positional and Locational Terms:

Superior (Cranial):

• Refers to a structure being closer to the head or higher than another structure.
• Example: The heart is superior to the stomach.

Inferior (Caudal):

• Refers to a structure being closer to the feet or lower than another structure.

Example: The stomach is inferior to the lungs.

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Anterior (Ventral):

• Refers to the front or towards the front of the body.
• Example: The chest is anterior to the spine.

Posterior (Dorsal):

• Refers to the back or towards the back of the body.

Example: The spine is posterior to the heart.

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• Medial: Refers to a structure being closer to the midline of the body.
• Example: The nose is medial to the ears.
• Lateral: Refers to a structure being farther from the midline of the body.

Example: The arms are lateral to the chest.

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Proximal: (Reference to the extremities only) Refers to a structure being closer to the root (point of attachment) of the limb than another structure in that limb Example: The elbow is proximal to the wrist.

Distal:(Reference to the extremities only) Refers to a structure being further away from the root (point of attachment) of the limb than another structure in the limb Example: The fingers are distal to the elbow.

Positions and Directions

• Ventral
• 
• Towards the front or belly
• 
• You Vent out or your nose and mouth.
• Dorsal
• 
• Towards the back
• 

Like the Dorsal fin of a dolphin.

Positions and Directions

• Prone
• 
• Lying face down
• 
• Like a Pro Baseball player sliding into Home.
• Supine
• 
• Lying face up
• 
• Lying on your spine and you can have soup poured into your mouth.
• Unilateral
• 
• Pertaining to one side of the body
• Bilateral
• 

Pertaining to both sides of the body

Anatomical Planes

Fixed lines of reference along which the body is often divided or sectioned to facilitate viewing of its structures Allow one to obtain a three-dimensional perspective by studying the body from different views

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• Superficial: Refers to a structure being closer to the surface of the body.

Example: The skin is superficial to the muscles.

Deep: Refers to a structure being farther from the surface of the body / Refers to a structure being closer to the core of the body than another structure Example: The bones are deep to the muscles.

Laterality Terms:

• Unilateral:
• Refers to something affecting or located on one side of the body.
• Example: A unilateral headache affects only one side of the head.
• Bilateral:
• Refers to something affecting or located on both sides of the body.

Example: Bilateral lung infection means both lungs are affected.

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• Ipsilateral:
• Refers to something occurring on the same side of the body.
• Example: The right arm and right leg are ipsilateral.
• Contralateral:
• Refers to something occurring on the opposite side of the body.

Example: The right arm and left leg are contralateral.

Terms for Body Movements:

• Flexion
• 
• Bending a joint or decreasing the angle between two bones
• 
• In the Fetal Position we are flexing our joints
• Extension
• 
• Straightening a joint or increasing the angle between two bones
• 
• In the Anatomical Position we are extending our joints
• Hyperextension
• 

Excessive extension of the parts at a joint beyond anatomical position.

Flexion / Extension / Hyperextension

Movements

• Adduction
• Moving a body part towards the midline of the body
• Abduction

Moving a body part away from the midline of the body

Movements

• Pronation
• Turning the arm or foot downward
• (palm or sole of the foot – down)
• 
• Prone
• Supination

• 
• (palm or sole of the foot
• up)

Supine

Movements

• Retraction
• 
• Moving a part backward
• Protraction
• 

• Elevation
• 
• Raising a part
• Depression
• 

Lowering a part

Movements

• Rotation
• 
• Turning on a single axis
• Circumduction
• 
• Tri-planar, circular motion at the hip or shoulder
• Internal rotation
• 
• Rotation of the hip or shoulder toward the midline
• External rotation
• 

Rotation of the hip or shoulder away from the midline

Movements

Lateral Flexion

 Side-bending left or right

Movements of the

• Foot
• Inversion
• 
• Turning the sole of the foot inward
• Eversion
• 
• Turning the sole of the foot outward
• Dorsiflexion
• 
• Ankle movement bringing the foot towards the shin
• Plantarflexion
• 

Ankle movement pointing the foot downward

Movements of the Wrist &

• Thumb

Radial Deviation

• 
• Movement of the wrist towards the radius or lateral side.

Ulnar Deviation

• 
• Movement of the wrist towards the ulna or medial side.
• Opposition
• 

Movement of the thumb across the palm of the hand.

Additional Range of Motion

EXPLAIN BODY REGION, CAVITIES AND ANATOMICAL PLANES

BODY REGION

The body can be divided into various regions, which help in identifying the location of injuries, illnesses, or treatments Head: This includes the skull, brain, eyes, ears, nose, and mouth. It is further divided into:

• Cranial region: Houses the brain.

Facial region: Includes the eyes, nose, mouth, and jaw.

Neck (Cervical region): Connects the head to the torso, containing vital structures like the trachea, esophagus, and cervical spine.

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• Torso (Trunk): This is the main body portion excluding the limbs and is subdivided into:
• Thoracic region (Chest): Includes the lungs, heart, and rib cage.
• Abdominal region: Contains the stomach, liver, intestines, and other digestive organs.

Pelvic region: Contains reproductive organs, bladder, and part of the large intestine.

Upper Extremities (Arms): This region includes the shoulders, arms, elbows, wrists, and hands.

Lower Extremities (Legs): Includes the hips, thighs, knees, ankles, and feet Back (Dorsal region): Refers to the spine and muscles along the posterior part of the body.

Abdominal Regions

Divided into nine (9) arbitrary regions projected onto the surface of the body by the following lines The subcostal

• Trans-tubercular planes
• The two mid-clavicular planes

These four planes establish the topographical divisions in the nine-region organization.

Abdominal regions

• Right hypochondrium
• Epigastric region
• Left hypochondrium
• Right groin (inguinal or iliac fossa region)
• Suprapubic region (hypogastrium),
• Left groin (inguinal region or iliac fossa)
• Middle the right flank (lumbar region)
• Umbilical region

Left flank (lumbar region)

Basic concepts of structural organization of human body

Horizontal transumbilical plane passes through the umbilicus and the intervertebral disc between vertebrae LIII and LIV and intersects with the vertical median plane to form four quadrants Right Upper Quadrant (RUQ)

• Left Upper Quadrant (LUQ)
• Right Lower Quadrant (RLQ)

Left Lower Quadrant (LLQ)

Basic body planes or sections

These terms are used for planes or sections that cut the body, organs, tissues, or cells

Anatomical Planes

• Sagittal plane

The plane dividing the body into right and left portions Midsagittal or median are names for the plane dividing the body into equal right and left halves

Anatomical Planes

• Frontal plane
• The plane dividing the body into front and back portions

Also called the Coronal plane

Anatomical Planes

• Transverse plane
• The horizontal plane dividing the body into upper and lower portions

Also called the Horizontal plane

Body planes and sections

• (also called XS – cross section)

(also called coronal)

Sectional Anatomy

• Describe three-dimensional structures.

Sectional Planes:

• Transverse Planes- divide the body into superior/inferior sections.

Frontal Planes/coronal plane – divide the body into anterior and posterior sections.

2. BODY CAVITIES

Body cavities: spaces within the body that help protect, separate and support internal organs.

• Body cavity is any fluid filled space in a multicellular organism.
• The two major cavities of the body are
• The dorsal cavity

The ventral body cavities.

The two major cavities of the body

The Dorsal Cavity

The dorsal body cavity is located near the posterior surface of the body and has two main subdivisions The vertebral canal that contains the spinal cord The cranial cavity that contains the brain

The Ventral Body Cavities

The ventral body cavity is located near the anterior surface of the body and has two subdivisions The thoracic cavity

The abdomino-pelvic cavity

The abdomino-pelvic cavity, which is separated by the diaphragm consists of two continuous cavities The abdominal cavity

The pelvic cavity

Organs-(Abdominal-Pelvic Cavity)

• Abdominal cavity contains
• Stomach
• Liver
• Gallbladder
• Pancreas
• Spleen
• small intestine
• Kidneys
• Appendix
• part of the large intestine.
• The pelvic cavity contains
• Part of the large intestine
• Rectum
• Urinary bladder
• Female reproductive organs (ovaries, uterine tubes, uterus, vagina)

Male reproductive organs (prostate, part of ductus deferens).

It is important to note that the testes and penis are not located in the ventral body cavity but are outside the body wall.

Thoracic Cavity and its Divisions

• Thoracic Cavity: Space enclosed by the ribs, sternum, and vertebral column
• The thoracic cavity is separated from the abdominal cavity by the diaphragm.
• This cavity contains three small cavities (potential spaces).
• The pericardial cavity (peri _around; cardia _ heart).
• Two pleural cavities (pleura _ side or rib).

The pericardial cavity surrounds the heart, and each pleural cavity contains a lung.

The Mediastinum

A broad central partition that separates the two laterally placed pleural cavities.

Extends from the sternum to the bodies of the vertebrae and from the superior thoracic aperture to the diaphragm.

The organs located in the mediastinum are the heart, thymus gland, oesophagus, trachea and bronchi.

The pleural cavities are located on either side of the mediastinum

Regions(subdivision) of mediastinum

• The middle mediastinum
• The superior mediastinum
• The anterior mediastinum

The posterior mediastinum

The middle mediastinum

• Centrally located in the thoracic cavity.
• Major Structures found
• heart,
• origins of the great vessels,
• various nerves

smaller vessels.

The superior mediastinum

The superior mediastinum is posterior to the manubrium of the sternum and anterior to the bodies of the first four thoracic vertebrae.

The superior mediastinum is continuous with the neck superiorly and with the inferior mediastinum inferiorly.

• The Major Structures found
• Thymus
• Right and left brachiocephalic veins
• Left superior intercostal vein
• Superior vena cava
• Arch of the aorta with its three large branches
• Trachea
• Esophagus
• Phrenic nerves
• Vagus nerves
• Left recurrent laryngeal branch of the left vagus nerve
• Thoracic duct

Other small nerves, blood vessels, and lymphatics

The anterior mediastinum

• Posterior to the body of the sternum
• Anterior to the pericardial sac.
• The posterior mediastinum
• Posterior to the pericardial sac and diaphragm
• Anterior to the bodies of the mid and lower thoracic vertebrae.
• Major structures in the posterior mediastinum
• Esophagus and its associated nerve plexus
• Thoracic aorta and its branches
• Azygos system of veins
• Thoracic duct and associated lymph nodes
• Sympathetic trunks

Thoracic splanchnic nerves

Peritoneum and Peritoneal Cavity

The peritoneum is the largest serous membrane in the body The abdominal cavity is lined by peritoneum, which consists of an epithelial-like single layer of cells (the mesothelium) together with a supportive layer of connective tissue.

• Two layers
• Parietal peritoneum lines the abdominal wall.
• Visceral peritoneum covers suspended organs
• The peritoneal cavity is a potential space between the parietal peritoneum

Contains a small amount of serous fluid

Basic concepts of structural organization of human body

Abdominal viscera are either intraperitoneal (organs are within the peritoneal cavity) or retroperitoneal (organs lie behind the peritoneum) Intraperitoneal structures are suspended from the abdominal wall by mesenteries Stomach

• Liver
• Gallbladder
• Spleen
• small intestine
• Appendix
• large intestine
• Rectum
• Urinary bladder
• Female reproductive organs (ovaries, uterine tubes, uterus, vagina)

Male reproductive organs (prostate, part of ductus deferens).

Basic concepts of structural organization of human body

Structures that are not suspended in the abdominal cavity by a mesentery and that lie between the parietal peritoneum and abdominal wall are retroperitoneal in position includes;

• The kidneys
• Ureters
• Pancreas

Great vessels

STRUCTURAL ORGANIZATION LEVELS OF HUMAN BODY