Skeletal System

Pelvic and Lower Limb Bones

The pelvic girdle and lower limb bones are essential for support, movement, and protection of internal organs. Understanding their features and differences is crucial for anatomical study.

• Pelvic Girdle Features: The pelvic girdle consists of the ilium, ischium, and pubis. Key features include the acetabulum (hip socket), obturator foramen, and pubic symphysis.

• Lower Limb Bones: The femur (thigh bone), patella (kneecap), tibia and fibula (leg bones), and bones of the foot (tarsals, metatarsals, phalanges) each have distinct anatomical landmarks.

• Sexual Dimorphism: Male and female pelves differ in shape; the female pelvis is generally wider and shallower to facilitate childbirth, while the male pelvis is narrower and deeper.

• Joints of the Lower Limb: Types include ball-and-socket (hip), hinge (knee), and gliding (ankle) joints.

Example: The femur articulates proximally with the acetabulum of the pelvis and distally with the tibia at the knee joint.

Lower Limb Muscles

Muscles of the lower limb are organized into compartments, each with specific functions and innervations.

• Compartments: The thigh has anterior, medial, and posterior compartments; the leg has anterior, lateral, and posterior compartments.

• Muscle Details: For each muscle, know the origin (where it starts), insertion (where it attaches), action (movement produced), and innervation (nerve supply).

Example: The quadriceps femoris group (anterior thigh) extends the knee and is innervated by the femoral nerve.

Lumbar and Sacral Plexus

Spinal Nerves and Plexuses

The lumbar and sacral plexuses are networks of nerves that supply the lower limb and pelvic region.

• Lumbar Plexus: Formed by spinal nerves L1-L4; major nerves include the femoral and obturator nerves.

• Sacral Plexus: Formed by spinal nerves L4-S4; major nerves include the sciatic, pudendal, and superior/inferior gluteal nerves.

• Major Nerves: Each nerve has a specific target area and function in the lower limb.

Example: The sciatic nerve is the largest nerve in the body and supplies most of the lower limb.

Skull / Skull Foramina / Cranial Nerves

Skull Bones and Sutures

The skull is composed of several bones joined by sutures, which are immovable joints.

• Major Skull Sutures: Coronal, sagittal, lambdoid, and squamous sutures connect the main bones of the skull.

• Facial Bones: Include the maxilla, zygomatic, nasal, mandible, and others. Each has distinct articulations and features.

• Cranial Bones: Include the frontal, parietal, temporal, occipital, sphenoid, and ethmoid bones.

Example: The coronal suture separates the frontal and parietal bones.

Cranial Nerves

Cranial nerves are twelve pairs of nerves that emerge directly from the brain and brainstem, each with specific functions.

• Foramina: Openings in the skull through which cranial nerves exit (e.g., optic canal for CN II, jugular foramen for CN IX, X, XI).

• Modality: Each cranial nerve may be sensory, motor, or both.

• List of Cranial Nerves:

  1. Olfactory (I)

  2. Optic (II)

  3. Oculomotor (III)

  4. Trochlear (IV)

  5. Trigeminal (V)

  6. Abducens (VI)

  7. Facial (VII)

  8. Vestibulocochlear (VIII)

  9. Glossopharyngeal (IX)

  10. Vagus (X)

  11. Accessory (XI)

  12. Hypoglossal (XII)

Example: The facial nerve (VII) exits the skull via the stylomastoid foramen and controls muscles of facial expression.

CNS - Brain

Development and Structure

The brain develops from five embryonic divisions and is organized into major subdivisions with specialized functions.

• Embryonic Divisions: Telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon.

• Major Subdivisions: Cerebrum, diencephalon, brainstem (midbrain, pons, medulla), cerebellum.

• Meninges: Three protective layers: dura mater, arachnoid mater, pia mater.

• Ventricles: Four interconnected cavities (lateral ventricles, third ventricle, fourth ventricle) containing cerebrospinal fluid (CSF).

• CSF Function: Cushions the brain, removes waste, and provides nutrients.

• Cerebral Lobes: Frontal, parietal, temporal, occipital, and insula; each lobe has distinct functions.

• Superficial Sulci: Major grooves that separate lobes, such as the central sulcus and lateral sulcus.

Example: The central sulcus separates the frontal and parietal lobes.

Autonomic Nervous System (ANS)

Organization and Function

The ANS regulates involuntary physiological functions and is divided into sympathetic and parasympathetic divisions.

• Autonomic vs. Somatic: The autonomic system controls involuntary actions (e.g., heart rate, digestion), while the somatic system controls voluntary muscle movements.

• Divisions: Sympathetic ("fight or flight") and parasympathetic ("rest and digest") systems differ in structure and function.

• Anatomical Components: Sympathetic nerves originate from thoracolumbar spinal cord; parasympathetic from craniosacral regions.

• Neurotransmitters: Acetylcholine and norepinephrine are the main neurotransmitters used by the ANS.

• Pathways: Each division has a two-neuron pathway: preganglionic and postganglionic neurons.

Example: The sympathetic division increases heart rate and dilates pupils, while the parasympathetic division slows heart rate and stimulates digestion.

Table: Comparison of Sympathetic and Parasympathetic Divisions

Additional info: The ANS also regulates glandular secretion, blood vessel diameter, and other homeostatic functions.