Pharynx
Structure and Function
Structure
The pharnyx is basically the joining of the nose and mouth (nasopharynx and oropharynx). It contains the hard palate (roof of the mouth) formed by the palatine bones, and the bottom of the maxillae. The soft palate is basically the uvula.
Functions:
Mechanism of swallow is controlled by a swallowing centre in the medulla oblongata and pons. Its initiated by touch receptors in the pharynx as a bolus of food reaches the back of the throat. This is what happens.
- The soft palate is pulled upwards, to stop food going into the nasal cavity, and some palatopharyyngeal folds close up, so only a small bolus can pass (preventing blockage later on)
- The larynx is pulled upwards towards the epiglottis, which passively shuts off its entrance, and the vocal cords get closer, narrowing the passageway between them.
- The respiratory centre of the medulla is directly inhibited by the swallowing centre, whilst the swallowing happens – deglutition apnoea (swallowing stop-of-inhalation)
- The Upper Oesophageal sphincter relaxes to let food pass, and then a sequence of striated constrictor muscles in the pharynx do some peristalsis.
Arterial and Venous supply
Nervous Supply
Mostly from the maxillary nerve, with the glossopharyngeal nerve supplying the soft palate.
Lymph
The lymph vessels drain directly into the deep cervical lymph nodes or indirectly into the retropharyngeal or paratracheal nodes
Histology
Line by non keratinising stratified squamous – basically identical to oesophagus
Clinical Conditions
Bulbar palsy
About: Weakness of the lower cranial nerves, usually caused by motor neurone disease, or demylenating conditions. Can be caused by surgery for acoustic neuroma, or radiotherapy for nasoharyngeal carcinomas.
Symptoms: Dysphagia, drooling, pooling of saliva in the pharynx and "a wasted fasciculating tongue". I think that means involuntary twitching.
Pseudobulbar palsy
About: Similar to bulbar, but the neurone defect is in the voluntary fibres. It is bilateral – and is sometimes seen following a capsular stroke – but because the cortico-bulbar fibres have bilateral innervations, sever only happen after bilateral infarcts.
Symptoms: The tongue is contracted and spastic – very different from bulbar.
Pharyngeal pouch
About: It's a diverticulum of the wall of the pharynx at "Killian's dehiscence", which is a triangle between the cricopharyngeous and inferior constrictor, which has no muscles behind it so it is weaker. At first the pouch is posterior, but ends up on one side (often left), where it shoves over the oesophagus.
Symptoms: Dysphagia, first mouthful easily swallowed, then further swallowing prevented, with regurgitation of pouch contents. Often palpable neck swelling, which may gurgle. Night time coughing.
Investigations: Barium Swallow. Do not endoscope, as it is fragile and can rupture.
Treatment: Surgical excision
Pharyngeal web
Basically I think it's a sort of lesion in the throat. Its pretty rare, and I couldn't find anything about it on the whole internet.
Schleroderma
About: Overproduction of collagen by cells, causing stiffening, lesions, infection etc. Can be localised on skin, or more widespread and systemic (which is pretty awful).
Symptoms: Gi problems, Dysphagia, Thickening of skin, pain and stiffness of joints, Raynaud's phenomenon (spasm of arteries supplying the fingers and toes).
Treatment: None. Ouch.