📖 Anatomy

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Anatomy

First pouch	Auditory tube, which comes in contact with epithelial line of first pharyngeal cleft, where future external acoustic meatus will form. Distal portion will form tympanic cavity (lining will become eardrum) Proximal portion will become auditory tube
Second pouch	Forms buds that penetrate surrounding mesenchyme, which together form the palatine tonsils
Third pouch	Forms thymus and inferior parathyroid glands
Fourth pouch	Forms superior parathyroid glands
Fifth pouch	Forms utlimobranchial body

Anatomy

The skull, the skeleton of the head, is the most complex bony structure in the body because it:

Encloses the brain, which is irregular in shape;
Houses the organs of special senses for seeing, hearing, tasting, and smelling; and
Surrounds the openings in to the digestive and respiratory tracts.

In the anatomical position, the skull is oriented so that the inferior margin of the orbit (eye socket) and the superior margin of the external acoustic meatus (auditory canal) are horizontal. This is called the orbitomenial plane (Frankfort plane).

The term cranium (L. skull) is sometimes used when referring to the skull without the mandible (lower jaw), but the cranium is often used when referring to the part of the skull containing the brain.
The superior part is the box-like structure called the calvaria (cranial vault, brain case); the remainder of the cranium, including the maxilla (upper jaw), orbits (eyeball sockets) and nasal cavities, forms the facial skeleton.
The term skullcap (calotte) refers to the superior part of the calvaria, which is removed during autopsies and dissections. The inferior aspect of the cranium is called the cranial base.

Anatomy

The Tongue

The tongue (L. lingua; G. glossa) is a highly mobile muscular organ that can vary greatly in shape.
It consists of three parts, a root, body, and tip.
The tongue is concerned with mastication, taste, deglutition (swallowing), articulation (speech), and oral cleansing.
Its main functions are squeezing food into the pharynx when swallowing, and forming words during speech.

Anatomy

Cartilage model is covered with perichondrium that is converted to periosteum
Diaphysis-central shaft
Epiphysis-located at either end of the diaphysis
Growth in length of the bone is provided by the emetaphyseal plate located between the epiphyseal cartilage and the diaphysis
Blood capillaries and the mesenchymal cells infiltrate the spaces left by the destroyed chondrocytes
Osteoblasts are derived from the undifferentiated cells; form an osseous matrix in the cartilage
Bone appears at the site where there was cartilage

Microscopic structure

Compact bone is found on the exterior of all bones; canceIlous bone is found in the interior
Surface of compact bone is covered by periosteum that is attached by Sharpey's fibers
Blood vessels enter the periosteum via Volkmann's canals and then enter the haversian canals that are formed by the canaliculi and lacunae
Marrow
- FiIls spaces of spongy bone
- Contains blood vessels and blood ceIls in various stages of development
- Types
Red bone marrow
- Formation of red blood ceIls (RBCs) and some white blood cells (WBCs) in this location
- Predominate type of marrow in newborn
- Found in spongy bone of adults (sternum, ribs, vertebrae, and proximal epiphyses of long bones)
Yellow bone marrow
- Fatty marrow
- Generally replaces red bone marrow in the adult, except in areas mentioned above
Ossification is completed as the proximal epiphysis joins with the diaphysis between the twentieth and twenty-fifth year