Branchial Arches

A lot of people, myself included, have trouble memorizing the development of the branchial apparatus. Hopefully with these mnemonics, this process will be much easier for you. It definitely helped me. Along with congenital heart disease, this seems to be the highest yield topic in Embryology for the USMLE Step 1.

1st Arch: a Massive list of M’s

Nerve: Maxillary and Mandibular nerves

Artery: Maxillary artery

Cartilage: Meckel’s Cartilage
- Mandible + sphenoMandibular ligament
- Malleus + Incus

Muscles: MAT x 2
- Muscles of Mastication
- Mylohyoid
- Anterior belly of digastric
- Anterior 2/3 of tongue
- Tensor veli palatini
- Tensor tympani

PS: for every one you get right reward yourself with an M&M  :D



2nd arch: Second

Nerve: Seventh nerve (facial nerve)

Artery: Stapedial artery and hyoid artery

Cartilage:
- Stapes
- Styloid
- Stylohyoid ligament
- leSSer horn of hyoid

Muscles:
- Muscles of facial expression (Smiling)
- Stapedius
- Stylohyoid
- poSSSterior belly of digastric



3rd arch: think Glossopharyngeal nerve

Nerve:
- Glossopharyngeal nerve

Cartilage:
- Greater horn of hyoid

Muscle:
- Stylopharyngeus



4th Arch: Swallowing + The exceptions to the 6th arch below

Nerve: Superior Laryngeal (branch of vagus)

Cartilage:
- Thyroid cartilage

Muscles:
- Pharyngeal constrictors
- Levator veli palatini
- Cricothyroid


6th Arch: Speaking (Laryngeal)

Nerve: Recurrent laryngeal (branch of vagus)

Cartilage: All laryngeal cartilages except thyroid cartilage

Muscles:  All instrinsic laryngeal muscles except cricothyroid

My Greatest Fear

Imagine waking up one morning only to discover that you're trapped in your body! You open your eyes to frantically discover that you're still alive. You role your eyes down to look towards your legs and they're still there, but unable to move. You're completely paralyzed, can't speak, can't yell for help...all you can do is move your eyes up and down. The only movement you have left in your body consists of vertical movements of the eyes because the only 2 nerves spared in this state are the oculomotor and trochlear nerves. You can hear yourself think, you can hear people around you speak, you can even understand what they're saying, but you're trapped! A prisoner of your own body. You can't express to anyone around you that you're scared to death or want to cry.

This is what is experienced by thousands of unlucky people with "Locked in syndrome" or cerebromedullospinal disconnection. It is caused by a lesion at the base of the pons such as an infarct of the basilar artery.

Corticospinal tracts are lost, meaning you have no movement in your body.
Corticobulbar tracts are lost, meaning that you have no movement in your face and can't speak. All you have are the up and down movements that you can perform using the oculomotor nerve.

This is the scariest disease to me. I would probably prefer to have any other disease than this.

Hypothalamus (hunger vs. satiety)

The hypothalamus has both the hunger center (lateral area) and the satiety center (ventromedial area).
I honestly didn't like the mnemonic in first aid for this. The mnemonic I like is this:
Lat makes you fat (hunger center)
Ven makes you thin (satiety center)

Brain Stem Lesions Simplified

I've been going through Anatomy these past few days A(for the second time now). I'm almost done. Neuroanatomy was the hardest section for me and took the most time. I despise the Brainstem section in Kaplan. I created a table to summarize the Brain stem lesions. It includes information from Kaplan, First Aid, and HY Neuroanatomy. It took time to create but it was worth it in the end.