File:Keith1902 fig151.jpg

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Fig. 151. Diagram of the Plica Semilunaris and Lachrymal Canaliculi

The plica semilunaris (Fig. 151), a fold of conjunctiva in the inner canthus of the eye, is a vestige of the third eyelid (membrana nictitans) which is so fully developed in birds and reptiles. It is well seen in the cat, partially crossing the cornea as the lids are shut. The lachrymal papillae rub in the grooves at the outer and inner margins of the fold.

The Lachrymal Gland arises as a number of epiblastic buds which spring from the fornix of the conjunctiva beneath the upper lid and grow into the tissue of the outer and upper segment of the orbit. The outer buds form the orbital part of the gland; the more internal buds form the palpebral part. Smaller lachrymal glands may occasionally be found at the •outer angle of the eye. This is the position occupied by the lachrymal glands of birds and reptiles (Wiedershiem). The lachrymal canaliculi and sac and nasal duct are formed out of" solid epithelial cords enclosed between the maxillary and lateral nasal processes (Fig. 151).

Development of Sense of Sight: Fig. 141. Elements of the Eyeball | Fig. 142. Invagination of Lens Vesicle | Fig. 143. Lens Vesicle | Fig. 144. Lens Fibres | Fig. 145. Optic Stalk and Vesicle 2nd month | Fig. 146. Optic Cup and Lens | Fig. 147. Optic Stalk and Cup | Fig. 148. Eye Parts from Mesoblast | Fig. 149. Eye and Orbit at birth | Fig. 150. Bones of the Orbit | Fig. 151. Plica Semilunaris and Lachrymal Canaliculi | Fig. 152. Motor Nerves of the Muscles of the Eye | Fig. 153. Foetal Brain 2nd month Optic Tracts | Fig. 154. Mesial Section of the brain of a Lizard | Fig. 155. Mesial Surface of the Brain 5th month | Fig. 156. Section of the Occipital Lobe | Fig. 157. Rudiment of the Occipital Lobe | Figures

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Human Embryology and Morphology (1902): Development or the Face | The Nasal Cavities and Olfactory Structures | Development of the Pharynx and Neck | Development of the Organ of Hearing | Development and Morphology of the Teeth | The Skin and its Appendages | The Development of the Ovum of the Foetus from the Ovum of the Mother | The Manner in which a Connection is Established between the Foetus and Uterus | The Uro-genital System | Formation of the Pubo-femoral Region, Pelvic Floor and Fascia | The Spinal Column and Back | The Segmentation of the Body | The Cranium | Development of the Structures concerned in the Sense of Sight | The Brain and Spinal Cord | Development of the Circulatory System | The Respiratory System | The Organs of Digestion | The Body Wall, Ribs, and Sternum | The Limbs | Figures | Embryology History


Keith A. Human Embryology and Morphology. (1902) London: Edward Arnold.

Cite this page: Hill, M.A. (2024, June 23) Embryology Keith1902 fig151.jpg. Retrieved from

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