Osteoology - mainly Pelvis Hip bone Normal basalis Mandible

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I now have all the content and images needed. Here is the comprehensive osteology study note:

Osteology - Study Notes

1. PELVIS

Gray's Anatomy for Students

The pelvis is a bony ring that links the vertebral column above to the lower limbs below. It is formed by three bones: the two hip bones (one on each side) and the sacrum posteriorly. The two hip bones articulate with each other anteriorly at the pubic symphysis (a cartilaginous joint) and with the sacrum at the paired sacroiliac joints (SI joints). Together these form a stable, near-rigid ring.

Pelvic inlet - anterior view showing pelvic bone, ala of sacrum, SI joint, inguinal ligament, and pelvic inlet (dashed red)

Pelvic Inlet (Superior Aperture)

The pelvic inlet (pelvic brim) separates the pelvis into:

Greater (false) pelvis - above the brim, part of the abdominal cavity
Lesser (true) pelvis - below the brim; the actual pelvic cavity

The pelvic inlet is bounded by:

Posteriorly: sacral promontory
Laterally: arcuate line of ilium + pectineal line of pubis
Anteriorly: upper border of pubic symphysis

Pelvic girdle with hip bone, sacrum, sacroiliac joints, pubic symphysis, and arcuate line

Pelvic Outlet (Inferior Aperture)

Bounded by:

Posteriorly: tip of coccyx
Laterally: ischial tuberosities and sacrotuberous ligaments
Anteriorly: inferior border of pubic symphysis, pubic arch (subpubic angle)

Communication with Lower Limb

Structures pass between pelvis and lower limb through two major routes:

Greater sciatic foramen (posterior) - transmits piriformis, sciatic nerve, superior/inferior gluteal nerves & vessels, pudendal nerve, internal pudendal artery
Obturator canal (anteriorly, through obturator foramen) - transmits obturator nerve and vessels
Lesser sciatic foramen - transmits obturator internus tendon; pudendal nerve and internal pudendal artery re-enter perineum here

Abdominal-Pelvic Continuity

The peritoneum of the abdominal cavity is continuous with that of the pelvic cavity. The pelvic inlet opens directly into the abdomen, so infections can spread freely between the two regions. The bladder expands superiorly from the pelvis into the abdomen, as does the uterus during pregnancy.

2. HIP BONE (Os Coxae / Innominate Bone)

Gray's Anatomy for Students; THIEME Atlas of Anatomy; Campbell-Walsh Urology

The hip bone (innominate bone) is formed by the fusion of three primary bones:

Ilium (upper fan-shaped part)
Ischium (posteroinferior)
Pubis (anteromedial)

All three meet at the acetabulum (hip socket):

Ilium: 2/5 of the acetabulum
Ischium: 2/5 of the acetabulum
Pubis: 1/5 of the acetabulum

The junction of all three bones in the acetabulum is marked in childhood by the triradiate (Y-shaped) cartilage, which fuses between ages 14-16 years.

Ilium

Large fan-shaped bone forming the upper part
Iliac crest - the superior curved border; extends from ASIS to PSIS
Anterosuperior iliac spine (ASIS) - attachment for inguinal ligament and sartorius
Anteroinferior iliac spine (AIIS) - attachment for rectus femoris
Posterosuperior iliac spine (PSIS) and posteroinferior iliac spine (PIIS)
Iliac fossa - medial concave surface; floor for iliacus muscle
Auricular surface - posteriorly; articulates with sacrum (SI joint)
Arcuate line - continues as pectineal line to form the pelvic brim
Greater sciatic notch - between PIIS and ischial spine

Ischium

Posteroinferior part of hip bone
Body of ischium - forms posteroinferior acetabulum
Ischial spine - projects medially; separates greater from lesser sciatic notch; attachment for sacrospinous ligament
Lesser sciatic notch - below ischial spine
Ischial tuberosity - weight-bearing prominence when sitting; attachment for sacrotuberous ligament and hamstrings (biceps femoris, semimembranosus, semitendinosus)
Ramus of ischium - joins inferior pubic ramus to complete the obturator foramen

Pubis

Anteromedial part of hip bone
Body - medial, bears pubic symphysis
Superior pubic ramus - projects laterally from body to acetabulum; bears the pectineal line (pecten pubis) and pubic tubercle
Inferior pubic ramus - descends and meets ischial ramus
The two pubic bones articulate at the pubic symphysis (secondary cartilaginous joint)

Obturator Foramen

Large opening bounded by the body and rami of the pubis and ischium. Closed in life by the obturator membrane, which leaves a small superior gap - the obturator canal - for the obturator nerve and vessels.

Key Ossification Points (Clinically Important)

Iliac crest fuses with ilium: by ~20 years
Ischial tuberosity fuses with ischium: by ~20 years
Triradiate cartilage of acetabulum: fuses between 14-16 years

3. NORMA BASALIS (Inferior View of Skull / External Cranial Base)

Gray's Anatomy for Students

The norma basalis is the view of the skull from below. It extends from the middle incisor teeth anteriorly to the superior nuchal lines posteriorly.

For descriptive purposes it is divided into three parts:

Anterior Part

Main features: teeth and hard palate

Teeth are anchored in the alveolar processes of the two maxillae, arranged in a U-shaped alveolar arch
Hard palate is formed by:
- Palatine processes of maxillae (anterior 2/3)
- Horizontal plates of palatine bones (posterior 1/3)
Sutures of hard palate:
- Intermaxillary suture - midline, between the two maxillae
- Palatomaxillary suture - between maxillae and palatine bones
- Interpalatine suture - midline, between the two palatine bones
Incisive fossa - anterior midline, behind the incisor teeth; contains incisive foramina (nasopalatine nerve and vessels)
Greater palatine foramina - near posterolateral border of hard palate (greater palatine nerve and vessels)
Lesser palatine foramina - just posterior to greater palatine foramina (lesser palatine nerves)
Posterior nasal spine - pointed projection at free posterior border of hard palate (palatoglossus and uvular muscles)

Middle Part (behind hard palate to anterior edge of foramen magnum)

Anterior half: vomer and sphenoid bones
Posterior half: occipital bone and temporal bones

Key features:

Choanae (posterior nasal apertures) - between vomer and medial pterygoid plates of sphenoid
Medial and lateral pterygoid plates of sphenoid - medial plate ends in pterygoid hamulus (around which tensor veli palatini wraps)
Scaphoid fossa - at root of medial pterygoid plate (origin of tensor veli palatini)
Pterygoid canal (Vidian canal) - opens just above scaphoid fossa (transmits Vidian nerve = greater petrosal + deep petrosal)
Foramen lacerum - irregular gap at junction of sphenoid, temporal, and occipital; filled with fibrocartilage in life (only internal carotid artery traverses its superior part)
Foramen ovale - transmits mandibular nerve (V3), accessory meningeal artery, lesser petrosal nerve
Foramen spinosum - transmits middle meningeal artery and meningeal branch of V3
Foramen rotundum - (opens into the middle cranial fossa, not visible from below)
Carotid canal - entrance for internal carotid artery
Jugular foramen - between temporal and occipital bones; transmits CN IX (glossopharyngeal), CN X (vagus), CN XI (accessory), and internal jugular vein
Styloid process + stylomastoid foramen (CN VII exits here) medial to mastoid process
Mastoid process - with mastoid notch (posterior belly of digastric)
Occipital condyles - articulate with atlas (C1); flanked by hypoglossal canal (CN XII)

Posterior Part (foramen magnum to superior nuchal lines)

Foramen magnum - largest foramen of skull; transmits medulla oblongata, vertebral arteries, anterior and posterior spinal arteries, spinal roots of CN XI
Pharyngeal tubercle - midline anteriorly on occipital bone; attachment of pharyngeal raphe (fibrous pharynx)
External occipital crest - midline ridge descending from foramen magnum to external occipital protuberance
External occipital protuberance (inion) - most prominent midline point
Superior nuchal lines - extend laterally from inion (trapezius, sternocleidomastoid)
Inferior nuchal lines - about 1 inch (2.5 cm) below superior nuchal lines

4. MANDIBLE

Gray's Anatomy for Students

The mandible is the bone of the lower jaw - the only moveable bone of the skull.

General Parts

Body - the horseshoe-shaped horizontal portion; formed by fusion of right and left halves at the mandibular symphysis (visible externally as a vertical midline ridge)
Rami - two vertical plates rising from the posterior body; one on each side
Angle of mandible - where inferior border of body meets posterior margin of ramus

Body of Mandible

Divided into:

Base (lower part) - contains the mental protuberance at the anterior midline, flanked by mental tubercles on each side
Alveolar part (upper part) - contains the alveolar arch with the teeth; resorbed when teeth are lost

External surface features:

Mental foramen - on lateral surface halfway between upper alveolar border and lower base; transmits mental nerve (terminal branch of inferior alveolar nerve) and mental vessels
Oblique line - continues posteriorly from the front of the ramus; attachment for muscles depressing the lower lip

Internal surface features:

Mental spines (genial spines) - 4 small spines in 2 pairs at midline, posterior to mandibular symphysis
- Superior pair: origin of genioglossus (into tongue)
- Inferior pair: origin of geniohyoid
Mylohyoid line - oblique ridge running posterosuperiorly from below the mental spines to below the last molar; attachment for mylohyoid muscle (floor of mouth)
Sublingual fossa - above the anterior 1/3 of mylohyoid line; houses sublingual gland
Submandibular fossa - below the posterior 2/3 of mylohyoid line; houses submandibular gland
Lingual nerve groove - shallow groove between last molar and mylohyoid line
Retromolar triangle - small triangular depression just posterior to last molar on medial upper surface; attachment for pterygomandibular raphe (which connects to buccinator/superior pharyngeal constrictor)

Ramus of Mandible

Coronoid process - anterior superior projection; attachment for temporalis muscle
Condylar process - posterior superior projection; participates in temporomandibular joint (TMJ) with the temporal bone
Mandibular notch (sigmoid notch) - between coronoid and condylar processes
Mandibular foramen - on medial surface of ramus; transmits inferior alveolar nerve and vessels into the mandibular canal; guarded anteriorly by the lingula (spine of Spix)
Pterygoid fovea - small depression anterior to condylar neck; attachment for lateral pterygoid muscle
Masseteric groove/tuberosity - on lateral surface at angle; for masseter
Pterygoid tuberosity - on medial surface at angle; for medial pterygoid

Ossification of Mandible

The mandible ossifies in membrane (intramembranous ossification) in association with Meckel's cartilage
The two halves fuse at the mandibular symphysis by the end of year 1 (early childhood)

Quick Reference Summary Table

Topic	Key Feature	Clinical Relevance
Pelvis - Inlet	Sacral promontory → arcuate line → pectineal line → pubis	Obstetric measurements
Hip bone	Triradiate cartilage fuses age 14-16	Paediatric hip X-ray interpretation
Hip bone - Ischium	Ischial tuberosity bears weight in sitting	Avulsion fractures in athletes
Hip bone - Obturator foramen	Closed by obturator membrane; obturator canal at top	Obturator hernia
Norma basalis - Middle	Foramen ovale (V3), spinosum (middle meningeal a.)	Trigeminal neurotomy, meningeal haemorrhage
Norma basalis - Posterior	Foramen magnum (medulla, vertebral arteries)	Tonsillar herniation
Norma basalis - Hypoglossal canal	CN XII	Hypoglossal nerve palsy
Mandible - Lingula	Guards mandibular foramen	Inferior alveolar nerve block landmark
Mandible - Mental foramen	Level of 2nd premolar, halfway up body	Dental anaesthesia
Mandible - Symphysis fusion	End of year 1	Age estimation in forensics

Sources: Gray's Anatomy for Students (9780323934237); THIEME Atlas of Anatomy - General Anatomy and Musculoskeletal System (9781626237186); Campbell-Walsh-Wein Urology (9780323546423)

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