Histology Textbook PDF

# Preface Histology is the study of tissues of the body and how these tissues are arranged to constitute organs. This subject involves all aspects of tissue biology, with the focus on how cell structure and arrangement optimizes functions specific to each organ. The purpose of this booklet is to he...

# Preface Histology is the study of tissues of the body and how these tissues are arranged to constitute organs. This subject involves all aspects of tissue biology, with the focus on how cell structure and arrangement optimizes functions specific to each organ. The purpose of this booklet is to help students to review the massive amount of material that comprises Histology. This educational resource has met the needs of learners for a well-organized and concise presentation of Histology that integrates the material with that of Biochemistry, Immunology, Endocrinology, Pathology and Physiology. The text is prepared specifically for students of Science as well as for advanced undergraduate courses in tissue biology. **The author** Dr. Salma S. Nassar # Tissues of the body There are four types of tissue in the body: - Epithelial tissue - Connective tissue - Muscular tissue - Nervous tissue ## 1- Epithelial tissue ### Characters of epithelia: 1. Origin: epithelia may arise from ectoderm or mesoderm or endoderm. 2. Matrix: (intercellular substance) is scanty but the epithelial cells may connect with each other by desmosomes. 3. Epithelium rests on a basement membrane which may be clear or not clear as in the transitional epithelia, olfactory epithelia, thyroid follicles and liver cells. 4. Epithelium having no blood vessels except endocrine glands. 5. Nerves can penetrate epithelia. 6. Epithelia can degenerate or regenerate. ### Types of Epithelial Tissue: - **Simple epithelium** (cells arranged in one layer). - **Compound (stratified) epithelium** (cells in more than one layer). - **Glandular epithelium** (cells forming secretory glands). - **Neuro-epithelium** (cells acting as receptors for stimuli). ## A- Simple epithelia ### Types: - Simple squamous. - Simple cuboidal. - Simple columnar. - Simple columnar ciliated. - Pseudo stratified columnar. - Pseudo stratified columnar ciliated. ### 1. Simple squamous epithelium It is of one layer of flat cells with flattened nuclei. It is present in the following sites: - Bowman's capsule of kidney. - Alveoli of lungs. - Endothelium of heart and blood vessels. - Serous membranes as pericardium, pleura and peritoneum. ### 2-Simple cuboidal epithelium Square cells with central rounded nuclei. It is found in: - Thyroid follicles and small ducts of glands. - Pigmented layer of retina and covering the eye lens. - Convoluted and small collecting tubules of kidney. ### 3-Simple columnar epithelium Tall cells with basal oval nuclei. It is present in: - Stomach wall secreting HCL. - Intestinal wall for absorption so they are covered with microvilli and phosphatase enzymes. - Lining gall bladder, common bile duct and pancreatic duct. - Lining the large collecting tubules of kidney. ### 4-Simple columnar ciliated Columnar cells with ciliated apices. Sites: - Vasa effrentia of testis. - Fallopian tube and uterus. - Upper end of Eustachian tube. ### 5- Pseudo-stratified columnar Columnar cells resting on a wavy basement membrane. The columnar cells are overlapping each other and so their uniformity. So their nuclei are arranged at different levels forming false rows. All the cells rest upon the basement membrane but some of them do not reach the surface. The surface may be ciliated or not. Cilia may be motile or non- motile. - **Pseudo stratified columnar:** ciliated with goblet cells and motile cilia. Present in: Respiratory passages (e. g, trachea and bronchi). - **Pseudo stratified columnar:** with non-motile cilia e.g, epididymis - **Pseudo stratified columnar:** (non- ciliated). Present in: Vas deferens, Large ducts of salivary glands and in the membranous part of male urethra.