Oral histology and embryology LO 1 part 2

Mesenchymal cells

Fibroblasts migrate to either side of the neural tube within the Somites. Differentiate into ——————— cells which differentiate into connective tissue forming cells, it: osteoblasts (bone) and chondroblasts (cartilage).

Mesodermal cells

The cells of this layer develop into: muscle, connective tissue proper, urinary system, reproductive system, cardiovascular system, lining of body cavity cavities.

Cartilage

The initial skeleton is made of:

Endochondral ossification

Cartilage skeleton is replaced by bone to offer rigidity and strength for muscle insertion. What is this process called?

Intramembranous bone formation.

bone tissue forms within a connective tissue membrane; ex. flat bones of the skeleton like the bones in the face and cranium. Connective tissue turns into bone.

Mesoderm

During the 10th week, myoblasts migrate from the myotomes following the segmental pattern of the skeleton. Myoblasts come from the ——————— layer.

Mesenchymal

——————— cells form the endothelial cells form the capillary cell. ———————- cells in the centre form the red blood cells.

Endodermal

——————— cells form elongated tube: linings of the digestive tract, respiratory tract, urinary tract. As well as the thyroid, parathyroids, thymus, liver, gallbladder, and pancreas.

Embryonic period

What period of pregnancy is known as the most critical period of prenatal development?

Ectoderm

The ————— is the first layer to form. Malformations in the ————— disrupts all other layers.

Dysplasia

——————— is another word for abnormal formation.

Treacher Collins syndrome

If there is a failure of migration of the neural crest cells to the facial region, this syndrome may develop in the embryo. this is also called mandibulofacial dysotosis.

Anodontia

One syndrome that can occur within the embryonic period is Ectodermal dysplasia which involves the abnormal development of one or more structures from the ectoderm. This condition may involve complete or partial ———————.

Rubella

This is an infective teratogen. Can result in cataracts, cardiac defects, and deafness.

Syphilis

This is another infective teratogen is the bacterial spirochete of ———————. It produces defects in the incisors (hutchinson's incisors) and molars (mulberry molars) as well as blindness, deafness, and paralysis.

Fetal alcohol syndrome

This is a pre and postnatal growth deficiency, intellectual deficiency, anomalies: low nasalbridge, small midface, widely spaced eyes with epicanthic folds, indistinct folds, indistinct philtrum and thin upper lip. Crowding of dentition, mouth breathing, and open bite. Caused by a teratogen.

Embryonic period

Fetal alcohol syndrome doesn't actually take place in the fetal period. What period does it take place in?

Spina bifida

This results from failure of fusion of the neural tube

Fetal period

This period is from the 9th week until the end of pregnancy.

Maturation

The fetal period encompasses the beginning of the ninth week to the ninth month, with the ——————— of existing structures occurring as the embryo is enlarging to become a fetus

Fetal period

In the ————— period, this process involves not only the physiological process of maturation of the individual tissue types and organs, but also proliferation, differentiation, and morphogenesis, as discussed before either the embryo.

Amniocentesis

The most common invasive prenatal diagnostic procedure to detect these malformations is ————————, where the amniotic fluid is sampled during the 14th to 16th week after the last missed menstrual period.

Placodes

Areas of specialized, thickened ectoderm from neural crest cells. These develop special sense organs.

Lens placodes

These are initially located on each side of the frontonasal process. The future eyes and related tissues.

Nasal placodes

These are thickened areas of the ectoderm that are superior to the stomodeum. Olfactory cells for the sensation of smell. ————— ——————— on the frontonasal process are the centre for the development of the nasal region and the nose. There is a depression in the center of each of these called a ————— pit.

Otic placodes

Laterally and posteriorly to the stomodeum. Future internal ear and related tissues.

Medial nasal processes

In week 6, the ————— ————— ——————— fuse together to form the root apex of the nose, philtrum of the lip, and the tubercle of the upper lip.

Alae

The lateral nasal processes form the ———— of the nose.

Nares (nostrils)

Fusion of the lateral nasal, maxillary, and medial nasal processes form the ———— of the nose.

Embryonic period.

Paranasal sinuses begin development in what period? This development continues into the fetal stage and after birth.

4-6

Development of the upper maxillary lip is form week — to week —. The upper lip is formed when bilateral maxillary processes fuse with each medial nasal processes. Due to underlying growth of the mesenchyme.

Maxillary processes and mandibular arch

Fusion of the sides of the developing oral cavity are from they ——————— processes and the ——————— arch. The area where these two meet is what forms the labial commissures.

Week 6

The maxillary process fuses with the lateral nasal process along the nasolacrimal groove. Ectodermal groove which canalizes (cell degeneration) to form the nasolacrimal duct. This duct drains the tears from the eye. What week does this occur in?

Cleft lip

Failure of fusion of the maxillary process with the medial nasal processes can result in ————— ———, with varying degrees of disfigurement and disability.

Commissural lip pits

Epithelium-lined blind tracts located at the labial commissures. May be shallow or several millimetres deep. Congenital ——— ———— may also be observed near the midline of the vermilion boarder. No tx necessary.

4th week

The development of the neck parallels the development of the face in time span. Beginning during the ——— week of prenatal development, within the embryonic period, and completed during the fetal period.

Primitive pharynx

The neck and its associated tissues develop from the ——————— ——————— and branchial apparatus.

Branchial arches.

In the fourth week, bilateral swellings of tissue appear inferior to the oral pit (stomodeum) and superior/adjacent to the heart bulge. This is how the ——————— ————— are formed (these are also called pharyngeal arches).

1,2,3,4,6

The 5 branchial arches are numbered:

Branchial arches

Five pairs of u-shaped tissue with mesenchyme (mesodermal core). Ectoderm covering, lined by endoderm. Give rise to important structures of the face and neck. Each of these paired ——————— has its own developing: cartilage, nerve components, vascular components, and muscular components within each mesodermal core.

First branchial groove

Within the fourth week, the ————— branchial arch develops into the external auditory canal.

LO 1-5