NEET MDS Lessons
Anatomy
Classified on functional Basis
Secretion ,Protection and waterproofing, Absorbtion, Transport, Sensory
Secretion
Glandular epithelium’s 3 types:
- Exocrine - with ducts
- endocrine - without ducts
- mixed exo-endocrine
Exocrine glands: One cell
- goblet cells
- In lining epitheliums of respiratory tract and GIT
- Secretes musin (protein) Musin + water = mucus, Mucus is a lubricant
More than one cell
Simple: Has a single duct,
- Acinar - mucus glands of the penile urethra
- Tubular - cripts of Lieberkuhn
- Coiled tubular - sweat gland
- Spiral tubular - Gland of Moll
- Branched tubular - mucous glands of the pyloric region
- Branched acinar - sebaceous gland in the skin
Compound
- Consists of a branched duct with numerous secretory end organs
- Compound tubular - Brünners glands
- Compound alveolar - mammary, prostate, pancreas, parotid
- Compound tubuloalveolar - submandibular-, sublingual salivary glands
Endocrine glands
Secrete directly into the blood
One cell : mast cells, in soft CT, near capillaries,
secrete - heparin - histamine
More than one cell
Cells can be arranged in the following ways:
- Cords - adrenal glands, parathyroid, anterior pituitary
- anastomosing cords with dilated blood capillaries in-between
- Isles - pancreas
- Follicles - thyroid
- cells line a follicle filled with non-cellular material
Innervation of the Pharynx
- The motor and most of the sensory supply of the pharynx is derived from the pharyngeal plexus of nerves on the surface of the pharynx.
- The plexus is formed by pharyngeal branches of the vagus (CN X) and glossopharyngeal (CN IX) nerves, and by sympathetic branches for the superior cervical ganglion.
- The motor fibres in the pharyngeal plexus are derived from the cranial root of accessory nerve (CN XI), and are carried by the vagus nerve to all muscles of the pharynx and soft palate.
- The exceptions are stylopharyngeus (supplied by CN IX) and the tensor veli palatini (supplied by CN V3).
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Pharyngeal Arch |
Arch Artery |
Cranial Nerve |
Skeletal elements |
Muscles |
|
1 |
Terminal Branch of maxillary artery |
Maxillary and mandibular division of trigemenial (V) |
Derived from arch cartilages (originating from neural crest): From maxillary cartilages: Alispenoid, incus From mandibular: Mackel’s cartilage, malleus
Upper portion of external ear (auricle) is derived from dorsal aspect of 1st pharyngeal arch.
Derived by direct ossification from arch dermal mesenchyme: Maxilla, zygomatic, squamous portion of temporal bone, mandible
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Muscles of mastication (temporalis, masseter, and pterygoids), mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini (originate from cranial somitomere 4) |
|
2 |
Stapedius artery (embryologic) and cortiotympanic artery (adult) |
Facial nerve (VII) |
Stapes, styloid process, stylohyoid ligament, lesser horns and upper rim of hyoid (derived from the second arch cartilage; originate from neural crest).
Lower portion of external ear (auricle) is derived from 2nd pharyngeal arch. |
Muscles of facial expression (orbicularis oculi, orbicularis oris, auricularis, platysma, fronto-ooccipitalis, buccinator), posterior belly of digastric, stylohyoid, stapedius (originate from cranial somitomere 6) |
|
3 |
Common carotid artery, most of internal carotid |
Glossopharyngeal (IX) |
Lower rim and greater horn of hyoid (derived from the third arch cartilage; originate from neural crest cells) |
Sytlopharyngeus (originate from cranial somitomere 7) |
|
4 |
Left: Arch of aorta; Right: Right subclavian artery; Original sprouts of pulmonary arteries |
Superior laryngeal branch of vagus (X) |
Laryngeal cartilages (Derived from the 4th arch cartilage, originate from lateral plate mesoderm) |
Constrictors of pharynx, cricothyroid, levator veli palatine (originate from occipital somites 2-4) |
|
6 |
Ductus arteriosus; roots of definitive pulmonary arteries |
Recurrent laryngeal branch of vagus (X) |
Laryngeal cartilages (derived from the 6th-arch cartilage; originate from lateral plate mesoderm) |
Intrinsic muscles of larynx (originate from occipital somites 1 and 2) |
The Hard Palate
- The anterior bony part of the palate is formed by the palatine process of the maxillae and the horizontal plates of the palatine bones.
- Anteriorly and laterally, the hard palate is bounded by the alveolar processes and the gingivae.
- Posteriorly, the hard palate is continuous with the soft palate.
- The incisive foramen is the mouth of the incisive canal.
- This foramen is located posterior to the maxillary central incisor teeth.
- This foramen is the common opening for the right and left incisive canals.
- The incisive canal and foramen transmit the nasopalatine nerve and the terminal branches of the sphenopalatine artery.
- Medial to the third molar tooth, the greater palatine foramen pierces the lateral border of the bony palate.
- The greater palatine vessels and nerve emerge from this foramen and run anteriorly into two grooves on the palate.
- The lesser palatine foramen transmits the lesser palatine nerve and vessels.
- This runs to the soft palate and adjacent structures.
->The two parietal bones (L. paries, wall) form large parts of the walls of the calvaria.
->On the outside of these smooth convex bones, there are slight elevations near the centre called parietal eminences.
->The middle of the lateral surfaces of the parietal bones is crossed by two curved lines, the superior and inferior temporal lines.
->The superior temporal line indicates an attachment of the temporal fascia; the inferior temporal line marks the superior limit of the temporalis muscle.
->The parietal bones articulate with each other in the median plane at the sagittal suture. The medial plane of the body passes through the sagittal suture.
->The inverted V-shaped suture between the parietal bones and the occipital bones is called the lambdoid suture because of its resemblance to the letter lambda in the Greek alphabet.
->The point where the parietal and occipital bones join is a useful reference point called the lambda. It can be felt as a depression in some people.
->In addition to articulation with each other and the frontal and occipital bones, the parietal bones articulate with the temporal bones and the greater wings of the sphenoid bone.
->In foetal and infant skulls, the bones of the calvaria are separated by dense connective tissue membranes at sutures.
->The large fibrous area where several sutures meet are called fonticuli or fontanelles.
->The softness of these bones and looseness of their connections at these sutures enable the calvaria to undergo changes of shape during birth called molding. Within a day or so after birth, the shape of the infant’s calvaria returns to normal.
->The loose construction of the new-born calvaria also allows the skull to enlarge and undergo remodelling during infancy and childhood.
->Relationships between the various bones are constantly changing during the active growth period.
->The increase in the size of the cranium is greatest during the first 2 years, the period of most rapid postnatal growth of the brain.
->The cranium normally increases in capacity until about 15 or 16 years of age; thereafter the cranium usually increases only slightly in size as its bones thicken for 3 to 4 years.
Stylohyoid Muscle
- Origin: Posterior border of the styloid process of the temporal bone.
- Insertion: Body of the hyoid bone at the junction with the greater horn.
- Nerve Supply: Facial nerve (CN VII).
- Arterial Supply: Muscular branches of the facial artery and muscular branches of the occipital artery.
- Action: Elevates the hyoid bone and base of the tongue.
|
Mesodermal Origin |
Muscles |
Innervation |
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Somitomeres 1, 2 |
Superior, medial and ventral recti |
Oculomotor (III) |
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Somitomere 3 |
Superior oblique |
Trochlear (IV) |
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Somitomere 4 |
Jaw-closing muscles |
Trigeminal (V) |
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Somitomere 5 |
Lateral rectus |
Abducens (VI) |
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Somitomere 6 |
Jaw-opening and other 2nd arch muscles |
Facial (VII) |
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Somitomere 7 |
Stylopharyngeus |
Glossopharyngeal (IX) |
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Somites 1, 2 |
Intrinsic laryngeals |
Vagus (X) |
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Somites 2-5 |
Tongue muscles |
Hypoglossal (XII) |