Discuss the embryological basis of branchial cyst/cervical cyst.
Answer.

• It is a congenital cyst (lined by ectoderm) that appears on the side of the neck along the anterior border of the sternocleidomastoid below and behind the angle of the mandible.
• It appears when 2nd, 3rd and 4th pharyngeal clefts fail to obliterate.

Hard Soft Palate

Embryological basis of branchial cleft cyst formation

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Describe the maxillary nerve under the following headings:

1. Origin,
2. Course and
3. Branches.
   

Answer.

Maxillary Nerve Origin and Course The maxillary nerve arises from the trigeminal ganglion in the middle cranial fossa. It passes forward and traverses the foramen rotundum to reach the upper part of the pterygopalatine fossa. From fossa, it enters the orbit by passing through the inferior orbital fissure.

As it enters the orbit, it is called the infraorbital nerve. In the orbit it first runs in the infraorbital groove, and then passes through the infraorbital canal, to finally appear on the face by emerging through the infraorbital foramen.

Origin of maxillary nerve from trigeminal nerve (CN V2)

Father of anatomy

Thus, the maxillary nerve traverses through four successive regions during its course:

1. Middle cranial fossa,
2. Pterygopalatine fossa,
3. Orbit and
4. Face.

Note: The infraorbital nerve is considered as the continuation of the maxillary nerve.

Purely sensory nature of maxillary nerve

Maxillary Nerve Branches

Branches of Maxillary Nerve

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Who is the father of anatomy? Briefly describe his life and achievements.
Answer.

Herophilus (325–280 BC) is considered the father of anatomy.

• He was a Greek physician and was regarded as the founder of the school of medicine at Alexandria, the then capital of Egypt. He taught anatomy in this medical school through vivisections (dissections of living humans) and dissections of human cadavers.
• Herophilus provided great descriptions of the skull, eye, various visceral organs, and their relationships. He also described the functional relationship of the spinal cord to the brain. Herophilus regarded the brain as the seat of intelligence and described many of its structures such as the cerebrum, cerebellum, and the 4th ventricle.

How Herophilus changed the study of anatomy

• He was the first to identify that nerves are either sensory or motor. He is also credited with the discovery of the ovum. Two monumental works of Herophilus were titled On Anatomy and On the Eyes.

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Question 1. What are the sites where red bone marrow is present in adults?
Answer.

The sites where red bone marrow is present in adults:

• Proximal ends of femur and humerus
• Ribs
• Sternum
• Skull
• Vertebrae
• Hip bone

Gross and microscopic structure of bone tissue

Question 2. What are the parts of a long bone?
Answer.

The long bone consists of the following parts:

• Epiphyses: Ends of a long bone that ossifies from secondary centres.
• Diaphysis: Shaft of a long bone that ossifies from a primary centre. It consists of an outer cortex of compact bone and an inner medullary cavity filled with bone marrow.

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Describe the external carotid artery in brief.
Answer.

Eternal Carotid Artery Origin and extent

• It is one of the two terminal branches of the common carotid artery.
• It extends from the level of the upper border of the thyroid cartilage to the back of the neck of the mandible, where it terminates by dividing into superficial temporal and maxillary arteries.

Origin of external carotid artery from common carotid artery

Branches

They are eight in number which corresponds to the number of alphabets in the term ‘EXTERNAL’, i.e. 8.

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Give the origin, insertion, nerve supply and actions of the occipitofrontalis muscle.
Answer.

The occipitofrontalis muscle along with epicranial aponeurosis forms the third layer of the scalp. This muscle consists of four bellies: two occipital bellies and two frontal bellies.

Occipitofrontalis Muscle Origin

Occipitofrontalis Muscle Occipital bellies: From lateral two-third of superior nuchal lines of the occipital bone.

Frontal bellies: From subcutaneous tissue of eyebrows and root of the nose where it blends with orbicularis oculi muscle.

Detailed anatomy of occipitofrontalis muscle of facial expression

Insertion Into epicranial aponeurosis (galea aponeurotica).

Nerve supply Posterior auricular and temporal branches of the facial nerve.

Occipitofrontalis Muscle Actions

• Moves the scalp forward and backwards by alternate contractions of frontal and occipital bellies.
• Occipital bellies draw the epicranial aponeurosis backwards, allowing the frontal bellies to contract, and cause transverse wrinkles in the skin of the forehead.

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Write a short note on the superficial temporal artery.
Answer.                                                                             

• It is the smaller terminal branch of the external carotid artery. It begins in the parotid gland behind the neck of the mandible.
• It runs vertically upwards across the root of the zygoma in front tragus. About 5 cm above the zygote, the artery divides into terminal anterior and posterior branches which supply the temporal fossa and scalp.

Terminal branch of external carotid artery anatomy

Superficial Temporal Artery Branches

• The transverse facial artery arises within the parotid gland and runs forward over the masseter muscle. It supplies TMJ, parotid gland and masseter muscle.
• Anterior auricular branch: It supplies the lateral surface of the auricle and part of the external auditory meatus.
• Middle (deep) temporal artery: It pierces the temporal fascia to supply the temporalis muscle.

Surface anatomy of superficial temporal artery pulse

• The zygomatic-orbital branch runs towards orbit along the upper border of the zygomatic arch.
• The anterior terminal branch runs forward towards the frontal tuberosity to supply soft tissues of the region. It often becomes noticeably tortuous in old age.
• The posterior terminal branch runs upwards, backwards and towards the occipital region to supply the soft tissues in the region.

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Give the origin, insertion, nerve supply and actions of the platysma.
Answer.

The platysma is a thin, quadrilateral, broad sheet of muscle in the superficial fascia of the side of the neck.

Platysma Origin From skin and deep fascia covering the pectoralis major and anterior part of the deltoid.

Platysma Insertion Into the lower border of the mandible and angle of mouth.

Superficial muscle of anterior neck anatomy

Platysma Nerve is supplied By the cervical branch of the facial nerve.

Platysma Actions

• Forms wrinkles in the skin of the neck
• Releases pressure of the skin on the underlying superficial veins of the neck to help in venous return
• Draws the angle of the mouth downward and laterally as seen clearly in the faces of marathon runners.

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What is cartilage?
Answer.

The cartilage is a specialized connective tissue, with a rubbery matrix (gel-like matrix) due to the deposition of proteoglycans which provides firmness along with elasticity to the skeletal framework of the body. Phylogenetically, it is older than the bone tissue.

Connective tissue characteristics of cartilage

• It is made up of a dense network of collagen or elastic fibres, which provide tensile strength to it.
• Its fibres are embedded in a firm, jelly-like amorphous substance made up of mucopolysaccharides, which allows the cartilage to bear weight without bending.
• It is firm in consistency and has elasticity.

Role of proteoglycans in cartilage structure

• It is an avascular tissue. The invasion of cartilage by blood vessels results in its calcification and death.
• It has no lymphatics.
• It is well adapted to coat the articular ends of the bone.

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Write a short note on cauda equina.

Answer. It is a leash of nerve roots of the lumbar (except L1), and sacral and coccygeal nerves around the filum terminale. It is called cauda equina because of its fancied resemblance to the tail of a horse (cauda = tail, equina = horse).

Clinical features of cauda equina syndrome in adults

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