Outline Of The Topic
Detailed outline of Axial Skeleton for General Anatomy - Anatomy And Histology - MBBS Pakistan Syllabus of First Professional Part I (Part 1), including what shall be covered, concepts clarified and common questions that shall be answered.
- Definition and Overview
- Main Components of the Axial Skeleton
- Skull
- Hyoid Bone
- Vertebral Column (Spinal Column)
- Thoracic Cage (Rib Cage)
- Axial Skeleton – Summary
- Clinical Integration & Surface Anatomy Importance
Affordable Paid Course Details For MBBS First Professional Part - I (Part 1) (For All Remaining Content/ Notes/ Videos and Much More)
Definition and Overview
Educate A Change Free Education Material | Detailed Notes For Preparation | Detailed Definitions, Concepts and Examples | Axial Skeleton For General Anatomy - Anatomy and Histology MBBS Pakistan Syllabus of First Professional Part I (Part 1) | General Anatomy | Free Education Material | Free Past Paper Tips and Tricks For MBBS Pakistan | Revision Notes | Topical Notes | Free Material By Hunain Zia (World Record Holder) | Best Notes To Excel In MBBS Exams
🔍 Definition and Overview
The skeletal system is the framework of bones and cartilage that supports the human body.
It is divided into two major components:
Axial skeleton (central core of the body)
Appendicular skeleton (limbs and girdles)
The axial skeleton forms the longitudinal axis of the body and is responsible for:
Supporting the head, neck, and trunk
Protecting the brain, spinal cord, and thoracic organs
Serving as an attachment point for muscles involved in movement, respiration, and posture
⚙️ Main Components of the Axial Skeleton
The axial skeleton consists of 80 bones, divided into the following four primary groups:
Skull (Cranial and Facial Bones) – 22 bones
Hyoid Bone – 1 bone
Vertebral Column (Spine) – 26 bones in adults (33 in early life)
Thoracic Cage (Rib Cage) – 25 bones (24 ribs + 1 sternum)
Let’s explore each component in deep detail below.
🧠 1. Skull
➤ Definition:
The skull is the bony structure of the head that protects the brain and supports facial structures.
➤ Classification:
The skull is divided into two major parts:
Cranial Bones (neurocranium) – Enclose the brain
Facial Bones (viscerocranium) – Form the structure of the face
➤ Cranial Bones (8 bones):
| Bone | Number | Function |
|---|---|---|
| Frontal | 1 | Forms the forehead and part of the orbital cavity |
| Parietal | 2 | Form the superior and lateral aspects of the skull |
| Temporal | 2 | Contain ear structures, form sides of the skull |
| Occipital | 1 | Forms the back and base of the skull, has foramen magnum |
| Sphenoid | 1 | Keystone bone that connects with all other cranial bones |
| Ethmoid | 1 | Forms part of nasal septum, roof of nasal cavity |
➤ Facial Bones (14 bones):
| Bone | Number | Function |
|---|---|---|
| Nasal | 2 | Bridge of the nose |
| Maxilla | 2 | Upper jaw, forms anterior hard palate |
| Zygomatic | 2 | Cheekbones |
| Mandible | 1 | Lower jaw, only movable skull bone |
| Lacrimal | 2 | House the lacrimal sac (tear duct area) |
| Palatine | 2 | Posterior part of hard palate |
| Inferior nasal conchae | 2 | Increase nasal cavity surface area |
| Vomer | 1 | Forms inferior part of nasal septum |
🧪 Clinical Relevance:
Fractures of cranial base may cause CSF rhinorrhea or otorrhea.
Craniosynostosis: Premature closure of skull sutures leads to skull deformities.
Temporomandibular Joint Dysfunction (TMJ): Jaw pain due to problems at the mandible-temporal junction.
Fontanelles in infants: Allow brain growth and help during childbirth. Closed by 18–24 months.
Keywords:
Hyoid Bone
Educate A Change Free Education Material | Detailed Notes For Preparation | Detailed Definitions, Concepts and Examples | Axial Skeleton For General Anatomy - Anatomy and Histology MBBS Pakistan Syllabus of First Professional Part I (Part 1) | General Anatomy | Free Education Material | Free Past Paper Tips and Tricks For MBBS Pakistan | Revision Notes | Topical Notes | Free Material By Hunain Zia (World Record Holder) | Best Notes To Excel In MBBS Exams
🦴 2. Hyoid Bone
➤ Definition:
A small, U-shaped bone located in the anterior neck between the mandible and larynx.
➤ Unique Feature:
The only bone in the human body that does not articulate with any other bone.
It is anchored by ligaments and muscles from the skull, mandible, tongue, and larynx.
➤ Functional Significance:
Supports the tongue and its movements.
Provides attachment for muscles of the floor of the mouth, tongue, larynx, and pharynx.
Essential in swallowing and speech production.
🧪 Clinical Relevance:
Fracture of the hyoid bone is rare and typically associated with manual strangulation – critical in forensic medicine.
Hyoid syndrome: Pain and tenderness around the hyoid region due to overuse or trauma.
Keywords:
Vertebral Column (Spinal Column)
Educate A Change Free Education Material | Detailed Notes For Preparation | Detailed Definitions, Concepts and Examples | Axial Skeleton For General Anatomy - Anatomy and Histology MBBS Pakistan Syllabus of First Professional Part I (Part 1) | General Anatomy | Free Education Material | Free Past Paper Tips and Tricks For MBBS Pakistan | Revision Notes | Topical Notes | Free Material By Hunain Zia (World Record Holder) | Best Notes To Excel In MBBS Exams
🌀 3. Vertebral Column (Spinal Column)
➤ Definition:
A flexible, segmented rod-like structure that forms the main axis of the skeleton.
Extends from the skull base to the coccyx.
Encloses and protects the spinal cord, supports the head, and serves as an attachment for ribs and muscles.
➤ Composition:
Originally 33 vertebrae:
7 Cervical (C1–C7)
12 Thoracic (T1–T12)
5 Lumbar (L1–L5)
5 Sacral (fused into sacrum)
4 Coccygeal (fused into coccyx)
In adults, sacral and coccygeal vertebrae are fused, resulting in 26 vertebrae.
📌 Regional Characteristics
🟣 Cervical Vertebrae (7)
Smallest and lightest vertebrae.
C1 (Atlas): Supports skull, allows nodding “yes”.
C2 (Axis): Has dens (odontoid process) – allows rotation “no”.
C7: Called vertebra prominens – long spinous process felt at the neck base.
🟡 Thoracic Vertebrae (12)
Each articulates with a pair of ribs.
Long, downward-pointing spinous processes.
Heart-shaped body.
🔵 Lumbar Vertebrae (5)
Largest and thickest vertebrae.
Bear the greatest body weight.
Kidney-shaped vertebral body.
🔴 Sacrum (5 fused)
Forms the posterior part of the pelvic cavity.
Has sacral foramina for passage of spinal nerves.
⚫ Coccyx (4 fused)
Vestigial tailbone.
Provides minor muscle and ligament attachment.
➤ Vertebral Curvatures
| Curvature | Direction | Type | Clinical Importance |
|---|---|---|---|
| Cervical | Convex anteriorly | Secondary | Develops after holding head up |
| Thoracic | Concave anteriorly | Primary | Present at birth |
| Lumbar | Convex anteriorly | Secondary | Develops after walking begins |
| Sacral | Concave anteriorly | Primary | Part of fetal development |
➤ Functions of Vertebral Column:
Protection: Encases the spinal cord.
Support: Provides upright posture and head support.
Flexibility: Enables movement and rotation.
Shock Absorption: Intervertebral discs cushion vertebrae.
🧪 Clinical Relevance:
Scoliosis: Abnormal lateral curvature.
Kyphosis: Exaggerated thoracic curve, often from osteoporosis.
Lordosis: Increased lumbar curvature; seen in pregnancy or obesity.
Herniated Disc: Nucleus pulposus protrudes through annulus fibrosus, compressing spinal nerves.
Spina Bifida: Neural tube defect where vertebral arch fails to close completely.
Keywords:
Thoracic Cage (Rib Cage)
Educate A Change Free Education Material | Detailed Notes For Preparation | Detailed Definitions, Concepts and Examples | Axial Skeleton For General Anatomy - Anatomy and Histology MBBS Pakistan Syllabus of First Professional Part I (Part 1) | General Anatomy | Free Education Material | Free Past Paper Tips and Tricks For MBBS Pakistan | Revision Notes | Topical Notes | Free Material By Hunain Zia (World Record Holder) | Best Notes To Excel In MBBS Exams
🦾 4. Thoracic Cage (Rib Cage)
➤ Definition:
The bony enclosure around the thoracic organs formed by the sternum, ribs, costal cartilages, and thoracic vertebrae.
➤ Structure:
| Component | Description |
|---|---|
| Ribs | 12 pairs (24 total) |
| Sternum | Flat bone divided into 3 parts: Manubrium, Body, Xiphoid process |
| Thoracic Vertebrae | 12 vertebrae (posterior attachment of ribs) |
➤ Ribs Classification:
| Type of Ribs | Pairs | Description |
|---|---|---|
| True Ribs | 1–7 | Directly attached to sternum via costal cartilage |
| False Ribs | 8–10 | Indirectly attached via cartilage of 7th rib |
| Floating Ribs | 11–12 | No anterior attachment |
➤ Sternum Anatomy:
Manubrium – Uppermost part, articulates with clavicles and first ribs.
Body – Middle and largest portion, receives costal cartilages of ribs 2–7.
Xiphoid Process – Inferior, cartilaginous in youth, ossifies with age.
➤ Functions of Thoracic Cage:
Protects vital organs: Heart, lungs, great vessels
Supports upper limbs: Via clavicle and scapula attachments
Facilitates respiration: Moves with muscles during inhalation and exhalation
Hematopoiesis: Sternum and ribs contain red bone marrow for blood formation
🧪 Clinical Relevance:
Rib fractures: Can puncture lungs (leading to pneumothorax or hemothorax)
Costochondritis: Inflammation of costal cartilage; causes chest pain
Sternal puncture: For bone marrow biopsy
CPR: Performed by compressing the lower half of the sternum
Keywords:
Axial Skeleton - Summary Table
Educate A Change Free Education Material | Detailed Notes For Preparation | Detailed Definitions, Concepts and Examples | Axial Skeleton For General Anatomy - Anatomy and Histology MBBS Pakistan Syllabus of First Professional Part I (Part 1) | General Anatomy | Free Education Material | Free Past Paper Tips and Tricks For MBBS Pakistan | Revision Notes | Topical Notes | Free Material By Hunain Zia (World Record Holder) | Best Notes To Excel In MBBS Exams
| Structure | Number of Bones | Key Functions |
|---|---|---|
| Skull | 22 | Protects brain, supports facial features |
| Hyoid Bone | 1 | Aids in speech, swallowing |
| Vertebral Column | 26 (adult) | Supports body, protects spinal cord |
| Rib Cage | 25 (12 pairs of ribs + sternum) | Protects thoracic organs, aids respiration |
Keywords:
Clinical Integration & Surface Anatomy Importance
Educate A Change Free Education Material | Detailed Notes For Preparation | Detailed Definitions, Concepts and Examples | Axial Skeleton For General Anatomy - Anatomy and Histology MBBS Pakistan Syllabus of First Professional Part I (Part 1) | General Anatomy | Free Education Material | Free Past Paper Tips and Tricks For MBBS Pakistan | Revision Notes | Topical Notes | Free Material By Hunain Zia (World Record Holder) | Best Notes To Excel In MBBS Exams
📌 Clinical Integration & Surface Anatomy Importance
Surface landmarks on axial skeleton aid in:
Venipuncture (e.g. using sternocleidomastoid landmarks for internal jugular vein)
ECG electrode placement using ribs/sternum
Lumbar puncture at L3–L4 interspace (safe zone below spinal cord)
Palpation of vertebra prominens (C7) to identify spine levels
Keywords:
Affordable Paid Course Details For Related Subjects
Related Free Education Posts
Affordable Paid Course Details
To get the latest content, updated and detailed notes, video lectures, live classes, quizzes, assignments personally marked by Sir Hunain (past paper based assignments) and much more, consider our paid courses.
MBBS First Professional Part – I (Part 1) Anatomy and Histology Crash Course Link: https://educateachange.com/courses/caie/pakistan-studies-2059-02-the-environment-of-pakistan-crash-corse/
MBBS First Professional Part – I (Part 1) Anatomy and Histology Full Scale Course Link: https://educateachange.com/courses/caie/pakistan-studies-2059-01-or-pakistan-studies-0448-01-the-history-and-culture-of-pakistan-o-level-or-igcse-full-scale-course/
Courses Page: https://educateachange.com/courses
Free Education
Check out more free material at our Free Education Section.
Free Education Link For This Particular Lesson’s Course (The Course Link Has All Lessons Related To This Subject/ Topic/ Course/ Unit Sorted In A Single Place – Updated Regularly With New Material Including Videos, Quizzes, Notes, Paper Practice and Much More): https://educateachange.com/o-level-pakistan-studies-2059-free-material/
https://educateachange.com/igcse-pakistan-studies-0448-free-material/
Free Material/ Education Link: https://educateachange.com/free-education-blog/
Free Course of MBBS First Professional Part – I (Part 1) Anatomy and Histology Link: https://educateachange.com/courses/anatomy-and-histology-mbbs-first-professional-part-i-part-1-free-course/
Free Courses Listing Link: https://educateachange.com/free-education
Ask Your Question Link: https://educateachange.com/ask-a-question
Social Media For Hunain Zia
YouTube: AYLOTI
Facebook: Official Facebook Page
Instagram: Official Instagram Page
LinkedIn: Official LinkedIn Profile
TikTok: Official TikTok Profile
Twitter: Official Twitter Profile
SnapChat: Offical SnapChat Account
Contact Information
Whats App: +92 336 311 1855
Email: free@educateachange.com
Free Education Groups
Facebook General Free Education Group: Real Free Education
Facebook CAIE Free Education Group: AYLOTI Education
Fair Usage Policy
NOTE: To ensure fair use and legal use of this material, please note the following: plagiarism, copying, saving, distribution, re-distribution, cross-posting and using this content on ANY other platform or website is prohibited.