Human Anatomy Course

Prostate Anatomy Made Simple 🧠 | High-Yield Medical Review

Understanding the prostate doesn’t have to be complicated.

This video covers:
✔ Anatomy (size, shape, relations)
✔ Zones vs lobes (what examiners LOVE to ask)
✔ Blood & nerve supply
✔ Clinical cases: BPH & prostate cancer

💡 Designed for medical students and exam prep.

👉 Watch, learn, and share with your colleagues!

Muscles of Mastication – Detailed Lecture Notes

The muscles of mastication are a group of skeletal muscles responsible for movements of the mandible required for chewing, speaking, and swallowing.
They are derived from the first pharyngeal (branchial) arch and are all supplied by the mandibular division of the trigeminal nerve (cranial nerve V3).

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Muscles Included

There are four main muscles of mastication:
1. Masseter
2. Temporalis
3. Medial pterygoid
4. Lateral pterygoid

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1. Masseter Muscle

A powerful, quadrangular muscle located on the lateral aspect of the mandible.

Origin
• Superficial part: zygomatic process of maxilla & anterior two-thirds of zygomatic arch
• Deep part: posterior one-third of zygomatic arch

Insertion
• Lateral surface of the ramus and angle of the mandible

Action
• Elevation of the mandible (primary muscle for closing the mouth)
• Superficial fibers assist in protrusion

Nerve Supply
• Masseteric nerve (branch of mandibular nerve – V3)

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2. Temporalis Muscle

A broad, fan-shaped muscle occupying the temporal fossa.

Origin
• Temporal fossa
• Deep surface of temporal fascia

Insertion
• Coronoid process of the mandible
• Anterior border of the ramus

Action
• Elevation of the mandible
• Posterior fibers cause retraction of the mandible

Nerve Supply
• Deep temporal nerves (branches of V3)

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3. Medial Pterygoid Muscle

A thick, quadrilateral muscle located on the medial side of the mandible, forming a functional sling with the masseter.

Origin
• Deep head: medial surface of lateral pterygoid plate
• Superficial head: maxillary tuberosity

Insertion
• Medial surface of the ramus and angle of the mandible

Action
• Elevation of the mandible
• Protrusion
• Unilateral contraction causes side-to-side grinding movements

Nerve Supply
• Nerve to medial pterygoid (V3)

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4. Lateral Pterygoid Muscle

A short, thick muscle with two heads, located in the infratemporal fossa.

Origin
• Superior head: infratemporal surface of greater wing of sphenoid
• Inferior head: lateral surface of lateral pterygoid plate

Insertion
• Neck of the mandible (pterygoid fovea)
• Articular disc and capsule of temporomandibular joint (TMJ)

Action
• Protrusion of the mandible
• Depression of the mandible (opening the mouth)
• Unilateral contraction causes contralateral deviation of the jaw

Nerve Supply
• Nerve to lateral pterygoid (V3)

Clinical Correlation
• Damage to CN V3 results in deviation of the jaw toward the side of the lesion
• Spasm or dysfunction of pterygoid muscles may cause TMJ disorders
• Hypertrophy of masseter is common in bruxism (teeth grinding)

🧠 Thyroid & Parathyroid Glands – Anatomy (Comprehensive Notes)

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🌟 1. THYROID GLAND — Overview

The largest endocrine gland in the body.
Produces: T3, T4 (metabolism) and calcitonin (calcium regulation).
Weight: ~20–25 g.

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📍 2. Location
• Lies in the anterior neck
• Deep to sternothyroid + sternohyoid muscles
• Extends from vertebral levels C5–T1
• Wraps around the trachea below the larynx

Parts:
• Right lobe
• Left lobe
• Isthmus → across 2nd–4th tracheal rings
• Pyramidal lobe (present in ~50%)

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🧩 3. Relations

Anterior:
• Strap muscles (sternohyoid, sternothyroid, omohyoid)

Posterolateral:
• Carotid sheath (CCA, IJV, vagus nerve)

Medial:
• Larynx
• Trachea
• Esophagus
• Recurrent laryngeal nerve (very important!)

Posterior:
• Parathyroid glands
• Prevertebral fascia

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🩸 4. Blood Supply

Arteries
• Superior thyroid artery (from external carotid)
• Inferior thyroid artery (from thyrocervical trunk → subclavian)
• Thyroid ima artery (variable, rare)

Veins
• Superior thyroid vein → IJV
• Middle thyroid vein → IJV
• Inferior thyroid vein → brachiocephalic vein

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🧠 5. Innervation

No secretomotor innervation—hormones regulate secretion.
• Sympathetic: cervical ganglia
• Parasympathetic: vagus
• Sensory: recurrent laryngeal nerve

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🔔 6. Lymphatic Drainage
• Prelaryngeal (Delphian) nodes
• Pretracheal nodes
• Paratracheal nodes
• Deep cervical nodes

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🧪 7. Parathyroid Glands — Overview

Small endocrine glands regulating calcium and phosphate via PTH.

Usually 4 glands:
• Superior pair (more constant position)
• Inferior pair (variable position)

Color: yellow-brown
Size: 6 × 3 × 1 mm

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📍 8. Location

On the posterior surface of the thyroid lobes:

Superior parathyroids:
• Constant
• Near the cricoid cartilage level

Inferior parathyroids:
• Variable
• May be found:
• Lower thyroid pole
• Thymus
• Anterior mediastinum

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🩸 9. Blood Supply

Same as thyroid:

Arteries:
• Mainly from inferior thyroid artery

Veins:
• Parathyroid veins → thyroid venous plexus

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🧠 10. Embryology (High-Yield)

Thyroid:
• From floor of primitive pharynx
• Migrates down → thyroglossal duct
• Foramen cecum = origin point

Parathyroids:
• Superior glands → 4th pharyngeal pouch
• Inferior glands → 3rd pouch (descend with thymus)

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🩺 11. Clinical Correlations

Goiter
• Enlarged thyroid
• Can compress trachea → dyspnea
• Dysphagia (esophageal compression)

Thyroidectomy

Risks:
• Injury to recurrent laryngeal nerve → hoarseness
• Injury to superior laryngeal nerve → voice pitch change
• Damage/removal of parathyroids → hypocalcemia
• Chvostek sign
• Trousseau sign

Ectopic thyroid tissue
• Lingual thyroid (most common)
• Along thyroglossal duct path

Parathyroid adenoma
• Causes hyperparathyroidism → kidney stones, bone pain (“stones, bones, groans”)

Facial Nerve Made Easy! All Muscles of Facial Expression (3D Anatomy Guide) Part 26

Facial Nerve Made Easy! All Muscles of Facial Expression (3D Anatomy Guide) Part 21

Facial Nerve Made Easy! All Muscles of Facial Expression (3D Anatomy Guide) Part 19