Anatomical Variants in Developmental Biology

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To improve surgical and radiological diagnosis

Through cadaveric dissections, radiology, and surgery

It does not influence the function of the affected body part

To improve medical diagnosis and treatment

Anatomical variants that do not affect body function

Anatomical variants are distinct from developmental abnormalities

Inadvertent entry into the pericardial or pleural cavities

1 in 10

Lambdoid suture

Injury, such as an ankle sprain

Cardiovascular system

Os Trigonum

Less than 50%

Buhler’s Arc

Bovine Arch

Less than 65%

More than 60%

Both blood vessel and nerve compression

Both reactive lymph nodes and malignant gastrointestinal tumors

The cardiovascular system

Both compression of the brachial plexus and subclavian vessels

All of the above

Cadaveric Dissections = Studying the abnormalities of the human body structure after death Radiology/Imaging = Using medical imaging techniques to visualize internal body structures Surgery = Incidental discovery during surgical procedures Medical History = Studying past medical records and patient history

Morphological fluctuations = Changes in organs or body parts that do not affect function Developmental abnormalities = Abnormalities that affect the function of the body part Congenital defects = Abnormalities present at birth that affect body function Anatomical variants = Changes in organs or body parts that do not affect function

Cadaveric Dissections = To identify anatomical variations in deceased individuals Radiology/Imaging = To diagnose anatomical variations in living individuals Surgery = To confirm anatomical variations during surgical procedures Medical History = To identify anatomical variations through patient history

Anatomical variants = Do not typically affect or hinder body function Developmental abnormalities = Affect the function of the body part Congenital defects = Present at birth and affect body function Morphological fluctuations = Result in a functional hindrance

Awareness of anatomical variants = To avoid complications during surgical procedures Importance of anatomical variants = To understand the normal range of human body structure Studying anatomical variants = To improve diagnostic accuracy Significance of anatomical variants = To understand the effects of morphological fluctuations

Incidental finding = Anatomical variant discovered during medical procedures Pathological condition = Anatomical variant that affects body function Functional hindrance = Anatomical variant that affects body function Spontaneous abortion = Anatomical variant that results in pregnancy termination

Cervical Rib = An extra rib that forms above the first rib, growing from the base of the neck just above the collarbone. Sternal Foramen = A developmental variant of the sternum resulting from incomplete fusion of the sternal ossification centers. Os Trigonum = An extra bone that sometimes develops behind the ankle bone (talus). Wormian Bones = Inconsistent bones in the body, usually near sites of ossification.

Cervical Rib = Thoracic outlet syndrome, causing pain, weakness, or tingling in the affected arm and fingers. Sternal Foramen = Complications during invasive procedures such as bone marrow aspiration or acupuncture. Os Trigonum = Os Trigonum Syndrome, triggered by an injury or repeated downward pointing of the toes. Wormian Bones = No known consequences, usually an incidental finding.

Cervical Rib = Neck region, above the first rib. Sternal Foramen = Sternum, resulting from incomplete fusion of the sternal ossification centers. Os Trigonum = Behind the ankle bone (talus). Wormian Bones = Skull, usually near the Lambdoid suture.

Cervical Rib = Present from birth, affecting around 1 in 10 people. Sternal Foramen = A developmental variant resulting from incomplete fusion of the sternal ossification centers. Os Trigonum = Connected to the talus by a fibrous band. Wormian Bones = Inconsistent bones in the body, usually near sites of ossification.

Cervical Rib = Thoracic outlet syndrome. Sternal Foramen = Complications during invasive procedures. Os Trigonum = Os Trigonum Syndrome, common among ballet dancers and athletes. Wormian Bones = Congenital disorders such as osteogenesis imperfecta and cleidocranial dysostosis.

Cervical Rib = An extra rib above the first rib. Sternal Foramen = A hole in the sternum. Os Trigonum = An extra bone behind the ankle bone (talus). Wormian Bones = Extra bones in the skull.

Accessory Soleus = An abnormal bronchus that comes directly off the lateral wall of the trachea Tracheal Bronchus = A condition in which splenic tissue is found outside the normal spleen Accessory Spleen = A muscular variation that may mimic a soft tissue tumour of the lower leg Circle of Willis = An arterial circle at the base of the brain

Muscular variations in the neck region = Pain, tickling sensation or other signs of impaired blood supply or nerve function Accessory Soleus = Compression of the brachial plexus and subclavian vessels Tracheal Bronchus = Diagnostic difficulties during physical examination or interpretation of imaging studies Accessory Spleen = Mimicry of a reactive lymph node or malignant gastrointestinal tumour

Thoracic outlet region = Compression of the brachial plexus and subclavian vessels Brain and heart circulation = Failure of catheterization due to radial artery anatomical variation Upper limb = Potential for failure of bone marrow aspiration or acupuncture Lower leg = Painful syndromes of the calf, ankle and foot

Macroscopically present Circle of Willis = Approximately 90% of cases Properly developed and symmetrical Circle of Willis = Less than 50% of individuals Normal arrangement of the branches of the arch of aorta = 65% of cases Bovine arch (arcus bovinus) = 27% of cases

Accessory Soleus = Asymptomatic, possibly presenting in the second to third decade of life Tracheal Bronchus = Often diagnosed via endoscopy or imaging Accessory Spleen = Usually asymptomatic, found as a part of investigations Buhler’s Arc or The arc of Buhler (AOB) = A rare anatomic variation

Vascular variants = Interventional cardiologists and plastic and reconstructive surgeons Muscular variations = Diagnostic difficulties during physical examination or interpretation of imaging studies Accessory bones = No specific importance mentioned Anatomical variants of the neck region = Catheterization and bone marrow aspiration or acupuncture

Accessory Spleen = Arises due to failure of fusion of one or more splenic lobules Tracheal Bronchus = Supplies ventilation to the upper lobe Accessory Soleus = May lead to blood vessel or nerve compression Circle of Willis = An arterial circle at the base of the brain

Accessory Spleen = Reactive lymph node or malignant gastrointestinal tumour Accessory Soleus = Soft tissue tumour of the lower leg Tracheal Bronchus = No specific misidentification mentioned Circle of Willis = No specific misidentification mentioned

Accessory Soleus = Lower leg Tracheal Bronchus = Lateral wall of the trachea Accessory Spleen = Outside the normal spleen Buhler’s Arc or The arc of Buhler (AOB) = Between the celiac artery and superior mesenteric artery

Buhler’s Arc or The arc of Buhler (AOB) = A rare anatomic variation Tracheal Bronchus = An asymptomatic anatomical variant Accessory Soleus = A muscular variation that may present in the second to third decade of life Accessory Spleen = A benign condition

Anatomical variants do not influence the function, whereas developmental abnormalities do.

They usually do not manifest as a pathological condition.

It is essential to be aware of variant anatomy to avoid misdiagnosis or misinterpretation.

Cadaveric dissections, radiology/imaging, and surgery.

Morphological fluctuations in organs or body parts that do not result in a functional hindrance.

To avoid misdiagnosis or misinterpretation, and to provide accurate diagnoses and treatment plans.

The primary concern is that the sternal foramen may be misinterpreted as an acquired defect, such as a fracture, and it is essential to be aware of it due to the proximity of the sternum to the pericardial and pleural cavities.

A cervical rib can compress nearby structures such as nerves or arteries, leading to thoracic outlet syndrome, which can cause pain, weakness, or tingling in the neck and arm, and can affect blood flow to the upper limb.

Os Trigonum Syndrome is a condition triggered by an injury, such as an ankle sprain, or repeated downward pointing of the toes, which is common among athletes, and it affects the extra bone that develops behind the ankle bone (talus), connected to the talus by a fibrous band.

Wormian bones are formed due to additional ossification centers in or near sutures of the flat bones of the human cranium, and they are associated with congenital disorders such as osteogenesis imperfecta, progeria, craniosynostosis, hypothyroidism, and cleidocranial dysostosis.

Anatomical variants in the cardiovascular system can increase the risk of complications during surgical procedures, and it is essential to be aware of them to prevent misinterpretation or injury to nearby structures.

An anatomical variant is a result of morphological fluctuations in organs or body parts that do not necessarily result in a functional hindrance, whereas a congenital defect is a pathological condition that affects the normal functioning of the body.

Understanding anatomical variants is crucial for interventional cardiologists and plastic and reconstructive surgeons to avoid complications during invasive procedures.

Although the Circle of Willis is macroscopically present in approximately 90% of cases, a properly developed and symmetrical Circle of Willis is found in less than 50% of individuals.

Accessory Soleus typically presents in the second to third decade of life, often mimicking a soft tissue tumor of the lower leg, and may be misidentified as a reactive lymph node or malignant gastrointestinal tumor.

Muscular variations, such as supernumerary muscles or additional heads of otherwise normal muscles, can lead to blood vessel or nerve compression, resulting in pain, tickling sensation, or other signs of impaired blood supply or nerve function.

The bovine arch (arcus bovinus) is the most common variant of the arch of aorta, and is characterized by the branching pattern of the arch of aorta similar to that found in bovines.

Less than 50% of individuals have a properly developed and symmetrical Circle of Willis.

Buhler's Arc (AOB) is a rare anastomotic vessel between the celiac artery and superior mesenteric artery, and is an important anatomical variant to be aware of.

Anatomical variants are normal morphological fluctuations in organs or body parts, whereas developmental abnormalities are pathological conditions that result from abnormal development.

Understanding anatomical variants, such as muscular variations in the neck region, is crucial for diagnosing and treating thoracic outlet syndrome, which can be caused by compression of the brachial plexus and subclavian vessels.

Understanding anatomical variants, such as accessory spleens, is crucial for accurate diagnosis and treatment of related conditions, as they can be misidentified as reactive lymph nodes or malignant gastrointestinal tumors.