WALDEYER’S LYMPHATIC RING

It is an uninterrupted circle of protective lymphoid tissue at the upper ends of the respiratory and alimentary tracts.

  • Also known as Nasal Associated Lymphoid Tissue (NALT).
  • Consists of the palatine, nasopharyngeal, lingual and tubal tonsils.
  • Produces B and T lymphocytes.
  • Involved in local defence.
  • Also produce lymphocytes to send to other lymph nodes.

PHARYNX

  • Length- 12cm
  • Width- 3.5cm in the upper portion and the lower portion of the pharynx is the narrowest portion of the GIT after the appendix.

Boundaries-

  • Superiorly- Base of the Skull
  • Inferiorly- Oesophagus
  • Posteriorly- Pre vertebral fascia
  • Anteriorly- Nasal cavity, Oral cavity, Larynx
  • Laterally- Medial pterygoid plate, Pterygomandibular raphe, Mandible, Tongue, Larynx, Thyroid and Cricoid cartilages, Middle ear cavity, Styloid process, CCA, ICA, ECA.

The pharynx is divided into 3 parts-

1.) Nasopharynx

  • Passage of air.
  • Located behind the nose.
  • Extends from the base of the skull to the soft palate.
  • Lines by ciliated columnar epithelium.
  • Supplied by pharyngeal branch of pterygopalatine ganglion.

2.) Oropharynx

  • Passage of food and air.
  • Extends from the soft palate to the epiglottis.
  • Lined by stratified squamous non keratinised epithelium.
  • Supplied by IX and X cranial nerves.

3.) Laryngopharynx

  • Passage of food.
  • Extends from the epiglottis to the cricoid cartilage.
  • Lined by stratified squamous non keratinised epithelium.
  • Supplied by the IX and X cranial nerves.

Muscles of the pharynx-

1.) Longitudinal Muscles

  • Stylopharyngeus
  • Palatopharyngeus – Makes the Passavant’s ridge
  • Salpingopharyngeus

2.) Circular Muscles

  • Superior constrictor
  • Middle constrictor
  • Inferior constrictor

The space between the base of the skull and the superior constrictor is called as the pharyngobasilar fascia or the SINUS OF MORGAGNI.

Killian’s dehiscence-

The inferior constrictor muscle splits into two- the stylopharyngeus and the cricopharyngeus.

The potential space between these two is called as the Killian’s dehiscence.

Incoordination in the area will lead to – ZENKERS DIVERTICULUM.

ProTaper Rotary File System

Developed in 2001 by- Dr. Cliff Ruddle, Dr. Pierre Machtou, Dr. John West, in cooperation with Dentsply Maillefer.

This system has 3 shaping and 5 finishing files.

Shaping files:-

  • Sx: 19/0.035
  • S1: 17/0.02
  • S2: 20/0.04

Finishing files:-

  • F1: 20/0.07
  • F2: 25/0.08
  • F3: 30/0.09
  • F4: 40/0.06
  • F5: 50/0.06

The cross section of all these files is convex triangular.

1.) Sx- Auxilliary shaping ProTaper file

  • No identification ring
  • Shorter in length: 19mm
  • Allows the shaping of coronal aspects of root canal and relocation of canal orifices in the direction of overhanging dentine area resulting in straight line access.

2.) S1, S2- Shaping ProTaper files

  • Purple and white identification rings respectively.
  • S1- to prepare the coronal one-third.
  • S2- to prepare the middle one-thirs.

3.) F1,F2,F3- Finishing ProTaper files

  • Yellow, red and blue identification rings respectively.
  • Each file has a fixed taper for the first 3mm and then a decreasing taper from D4 to D16. This:
    • Ensures continuous flexibility withing the file.
    • Avoids too large diameter at the shaft area of the instrument.
    • Reduces the potential for dangerous taper lock.
    • Enhances the strength of the file.

4.) F4,F5- Finishing ProTaper files:

  • Help in the apical preparation of larger canals.
  • F4 has 2 black rings and F5 has 2 yellow rings.
  • The body of both the files has a progressively decreasing taper and hence ensures excellent flexibility.

CYTOKINES

Cytokines are soluble protiens/polypeptides, produces by a variety of hematopoetic and non hematopoetic cell types. They are responsible for the regulation of immunological, inflammatory and reparative host responses.

Cytokines tend to bind to high affinity receptors and the target cells and mediate their effects. Specific cytokines mediate specific reactions.

Reference: Arvind Arora

Cytokines basically mediate immune response. But some cytokines are also pro inflammatory.

These are:-

Il-1, TNF alpha and IL-6.

IL-1 is the most important pro inflammatory cytokine.

Anti inflammatory cytokines are involved in the resolution of inflammation. These include:

IL-4, IL-10 IL-13 and TGF beta.

IL-4 has mainly anti-inflammatory properties with some pro-inflammatory properties.

TGF-beta is the most important fibrogenic factor.

T- Cells

T- cells are among the two important cells of the adaptive immune system (others are B- Cells). T-cells arise in the bone marrow and mature in the thymus.

T- cells constitute 60-70% of the circulating peripheral lymphocytes.

T- cells categories:-

1.) Helper or Inducer T-cells:

60% of T- cells are helper T- cells. They have CD4 surface marker and are MHC II restricted. Types of CD4 helper cells are:

A) Effector cells- TH1, TH2 and TH17 cells. The TH1 cells are activated by IFN- gamma and themselves produce IL-2, IFN-gamma and IL-12. They are the primary cells involved in delayed hypersensitivity, cell mediated immunity, macrophage activation and killing of intracellular microbes. TH2 cells are activated by IL4 and themselves produce IL4, IL5, IL6 and IL13. They produce all antibodies except for IgG2b and also provide defence against helminthic parasites. TH17 cells are powerful recruiters of neutrophils and monocytes to play a role in severe inflammatory diseases.

B) Memory cells- They retain the antigenic affinity of previously activated T-cells and are used in a second immune response.

2.) Cytotoxic T-cells:

30% of the total T-cells. They have CD8 surface marker and MHC I restricted. They kill amd lyse target cells which include tumour cells, virus infected cells and allograft.

THE RATIO OF CD4:CD8 T-cell is normally 2:1.

3.) Suppressor T-cells:

They have CD8 surface marker and are MHC I restricted. They are responsible for down regulation of the immune response.

TCELL RECEPTOR (TCR)

TCR is a molecule found on the T-cell which is responsible for recognising the antigen bound to MHC molecule. It is a heterodomer made up of an alpha and a beta chain. The presence of TCR gene rearrangements demonstrated by molecular analysis is a marker of T-cell lineage.