NEET MDS Lessons
Anatomy
EPITHELIUMS
Epithelial Tissue Epithelial tissue covers surfaces, usually has a basement membrane, has little extracellular material, and has no blood vessels. A basement membrane attaches the epithelial cells to underlying tissues. Most epithelia have a free surface, which is not in contact with other cells. Epithelia are classified according to the number of cell layers and the shape of the cells.
- Epitheliums contain no blood vessels. There is normally an underlying layer of connective tissue
- Almost all epitheliums lie on a basement membrane.The basement membrane consists of a basal lamina and reticular lamina. The reticular lamina is connected to the basal lamina by anchoring fibrils. The reticular lamina may be absent in which case the basement membrane consist only of a basal lamina. The basal lamina consists of a - lamina densa in the middle (physical barrier) with a lamina lucida on both sides (+charge barrier),The basement membrane is absent in ependymal cells.The basement membrane is not continuous in sinusoidal capillaries.
- Epitheliums always line or cover something
- Epithelial cells lie close together with little intercellular space
- Epithelial cells are strongly connected to one another especially those epitheliums that are subjected to mechanical forces.
Functions of Epithelium:
→ Simple epithelium involved with diffusion, filtration, secretion, or absorption
→ Stratified epithelium protects from abrasion
→ Squamous cells function in diffusion or filtration
The Palate
- The palate forms the arched roof of the mouth and the floor of the nasal cavities.
- The palate consists of two regions: the anterior 2/3 or bony part, called the hard palate, and the mobile posterior 1/3 or fibromuscular part, known as the soft palate.
The Lips
- These are mobile muscular folds that surround the mouth, the entrance of the oral cavity.
- The lips (L. labia) are covered externally by skin and internally by mucous membrane.
- In between these are layers of muscles, especially the orbicularis oris muscle.
- The upper and lower lips are attached to the gingivae in the median plane by raised folds of mucous membrane, called the labial frenula.
Sensory Nerves of the Lips
- The sensory nerves of the upper and lower lips are from the infraorbital and mental nerves, which are branches of the maxillary (CN V2) and mandibular (CN V3) nerves.
The Inferior Wall of the Orbit
- The thin inferior wall of the orbit or the floor is formed mainly by the orbital surface of the maxilla and partly by the zygomatic bone, and orbital process of the palatine bone.
- The floor of the orbit forms the roof of the maxillary sinus.
- The floor is partly separated from the lateral wall of the orbit by the inferior orbital fissure.
The Palate
- The palate forms the arched roof of the mouth and the floor of the nasal cavities.
- The palate consists of two regions: the anterior 2/3 or bony part, called the hard palate, and the mobile posterior 1/3 or fibromuscular part, known as the soft palate.
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.
Ligaments of the Joint
- The fibrous capsule is thickened laterally to form the lateral (temporomandibular) ligament. It reinforces the lateral part of this capsule.
- The base of this triangular ligament is attached to the zygomatic process of the temporal bone and the articular tubercle.
- Its apex is fixed to the lateral side of the neck of the mandible.
- Two other ligaments connect the mandible to the cranium but neither provides much strength.
- The stylomandibular ligament is a thickened band of deep cervical fascia.
- It runs from the styloid process of the temporal bone to the angle of the mandible and separates the parotid and submandibular salivary glands.
- The sphenomandibular ligament is a long membranous band that lies medial to the joint.
- This ligament runs from the spine of the sphenoid bone to the lingula on the medial aspect of the mandible.
Connective Tissue
Functions of Connective tissue:
→ joins together other tissues
→ supporting framework for the body (bone)
→ fat stores energy
→ blood transports substances
Connective tissue is usually characterized by large amounts of extracellular materials that separate cells from each other, whereas epithelial tissue is mostly cells with very little extracellular material. The extracellular substance of connective tissue consists of protein fibers which are embedded in ground substance containing tissue fluid.
Fibers in connective tissue can be divided into three types:
→ Collagen fibers are the most abundant protein fibers in the body.
→ Elastic fibers are made of elastin and have the ability to recoil to original shape.
→ Reticular fibers are very fine collagen fibers that join connective tissues to other tissues.
Connective tissue cells are named according to their functions:
→ Blast cells produce the matrix of connective tissues
→ Cyte cells maintains the matrix of connective tissues
→ Clast cells breaks down the matrix for remodeling (found in bone)