3B: ORGANOLOGY

• Organs are aggregates of tissues performing a specific function.
• The study of organs constitutes the science of organology.
• Frog’s Skin

  • there are 2 distinct layers: outer epidermis and the inner, thick layer, the dermis
  • Epidermis: consists of stratified epithelium
  • Stratum Corneum: The outermost layer of the epidermis made of dead, flattened cells that are shed by the animal.
  • Stratum Germinativum: located beneath the stratum corneum, are layers of cuboidal to columnar cells and cells are actively diving to replace cells in stratum corneum
• Frog’s skin

  • Dermis is divided into 2 layers
  • The outer stratum spongiosum (stratum laxum): is composed of loosely arranged connective tissue fibers and abundant blood vessel s
  • Melanosphores or black pigment cells are seen in the junction of this layer with the stratum spongiosum
  • This layer contains abundant mucous glands and they open to the surface by means of a neck extending through the epidermis
  • Stratum compactum: inner layer of the dermis and consists of white fibrous connective tissue running parallel to the surface of the skin
• Frog’s Skin

  • Subcutaneous tissue or hypodermis: Under the dermis is a connecting layer made up of loose connective tissue and adipose that anchors the skin to the tissue membrane; not considered part of the skin
• Frog’s stomach and small intestine

  • Rugae: folds in the inner wall of the stomach which projects into the cavity of the organ
  • Villi: exhibits thinner folds in the intenstine
• Tunica mucosa: thrown into folds onto the lumen. Consists of:

  1. Simple columnar epithelium: in the small intestine, goblet cells may be seen among the columnar cells. Goblet cells are absent in the stomach
  2. Lamina propria: a connective tissue layer containing glands and blood vessels
  3. Muscularis mucosa: thin layer of muscle
• Submucosa

  • beneath the mucosa
  • made of connective tissues containing glands, blood vessels and nerves
• Tunica Muscularis:

  • thick layer of circular and longitudinal smooth muscles
• Serosa:

  • The outermost layer of loose connective tissue covered by a layer of mesothelium
• Blood Vessels

  1. Tunica intima: lining epithelium of the vessel and a layer of elastic tissue in wavy appearance.
  2. Tunica media: intermediate layer made of smooth muscle, collagenous and elastic fibers, and connective tissue cells. Compare this layer in the artery and vein.
  3. Tunica externa / adventitia: external layer in which the elements include external elastic membrane, collagenous and elastic fibers, blood vessels, and loose connective tissue
• Spinal Cord

  • Central canal: small cavity at the center,
  • Ependymal Cells: columnar cells surrounding the canal
  • Gray matter: outer of the central canal, resembles the letter “H”; consist of nerve cells, neuroglia, naked fibers, and blood vessels
  • White matter: outer to the gray matter is a lightly stained portion that is composed of nerve fibers
  • Pia mater: thin sheath of connective adhering t the cord
  • Dura mater: outer to the pia mater, which is in contact with the braincase