HISTOLOGY, CYTOLOGY AND EMBRYOLOGY (a course of lectures) CONTENTS: Lecture 1. Origin and Subiect Matter of Histology (V.L. Goryachkina) 2 Lecture 2. Membranous and Nonmembranous Organelles (V.L .Goryachkina) 5 Lecture 3. Nucleus and Cell Cycle (V.L. Goryachkina) 8 Lecture 4. Introduction to Tissues and Tissue Development. Initial Stages of Embryonic Development (T.V. Boronikhina) 10 Lecture 5. Epithelial Tissue (S.L. Kuznetsov) 13 Lecture 6. Blood and Lymph (T.V. Boronikhina) 17 Lecture 7. Connective Tissues (V.L. Goryachkina) 21 Lecture 8. Cartilage and Bone (T.V. Boronikhina) 26 Lecture 9. Muscle Tissues (V.L. Goryachkina) 30 Lecture 10. Nervous Tissue – I (S.L. Kuznetsov) 33 Lecture 11. Nervous Tissue – II (S.L. Kuznetsov) 35 Lecture 12. Nervous System – I (S.L. Kuznetsov) 37 Lecture 13. Nervous System – II (S.L. Kuznetsov) 39 Lecture 14. Primary Sentient Sense Organs: The Eye and the Organ of Smell (T.V. Boronikhina) 41 Lecture 15. Secondary Sentient Sense Organs: The Ear and the Organ of Taste (T.V. Boronikhina 46 Lecture 16. Cardiovascular System – I (V.L. Goryachkina) 49 Lecture 17. Cardiovascular System – II (V.L. Goryachkina) 52 Lecture 18. Central Organs of Hemopoiesis: Red Bone Marrow and Thymus(V.L. Goryachkina) 56 Lecture 19. Peripheral Organs of Hemopoiesis and Immunogenesis (V.L. Goryachkina) 60 Lecture 20. Endocrine System – I (S.L. Kuznetsov) 63 Lecture 21. Endocrine System – II (S.L. Kuznetsov) 66 Lecture 22. Gastrointestinal Tract – I (S.L. Kuznetsov) 69 Lecture 23. Gastrointestinal Tract – II (S.L. Kuznetsov) 72 Lecture 24. Gastrointestinal Tract – III (S.L. Kuznetsov) 74 Lecture 25. Respiratory System (V.L. Goryachkina) 76 Lecture 26. Integumentary System: Skin and Its Appendages (V.L. Goryachkina) 79 Lecture 27. Urinary System (S.L. Kuznetsov) 83 Lecture 28. Male Reproductive System (T.V. Boronikhina) 86 Lecture 29. Female Reproductive System – I (T.V. Boronikhina) 90 Lecture 30. Female Reproductive System – II (T.V. Boronikhina) 94 Lecture 31. Human Embryology – I (T.V. Boronikhina) 98 Lecture 32. Human Embryology – II (T.V. Boronikhina) 101 Lecture 1 The Origin and the Subiect Matter of Histology (V.L. Goryachkina) From its derivation, the word “histology” (the Greek histos – tissue, logia – study or science of) means the science of tissues. But what is a tissue? This was derived from the French tissu, which means a weave or texture. It was introduced in the language of biology by Bichat (1771-1802). He wrote a book on the tissues of the body, in which he named more than 20 tissues. However, he did not use the microscope to classify them. Seventeen years after Bichat’s death the term “histology” was coined by the microscopist Meier, who used microscopy for describing tissues. It was established that there were only four basic tissues: epithelium, connective tissue, muscle tissue, and nervous tissue. In the 17th century Robert Hooke built a compound microscope. He examined a thin slice of cork and observed that it was composed of tiny empty compartments. He named the small compartmenTS-cells. Subsequently, other biologists studied plant tissue with a microscope, and it became obvious that in living plants the small compartments contained a little jelly-like body. Furthermore, as animal tissues were studied by microscopy, it became obvious that they were composed of tiny jelly-like bodies. So by 1839, the cell doctrine was postulated independently by Schleiden and Schwann. The microscope revealed the cell to have two main parts. Living cells have a more or less central part. This central part was named its nucleus (the Latin nux - nut), because it reminded of a nut lying in the center of its shell. For the same reason the Greek prefix “kary” (the Greek karyon - nut) may also be used in words with reference to the nucleus. For example, the dissolution of the nucleus as a cell dies is called karyolysis (the Greek lysis denotes dissolution). A membrane was seen to enclose the nucleus, and it was named the nuclear membrane or envelope. One or more rounded, dark-staining bodies in the interior of the nucleus were each called a nucleolus. Tiny granules or clumps of dark-staining material scattered about within the nucleus were called chromatin (the Greek chrom – color) because of their affinity for certain dyes. The outer and generally larger part of the cell was called cytoplasm (the Greek “kytos” denotes something that is hollow or that covers; plasma, something molded). Now it is known that the cytoplasm contains organelles. These organelles lie suspended in the cytoplasmic matrix or cytosol. With the advent of electron microscopy it became possible to observe the cell membrane itself. The cell membrane received the name plasmalemma (derived from the Greek lemma meaning bark) for its resemblance to the bark of trees. Cytoplasm The cytoplasm contains organelles (they are constant structures of the cells) and inclusions (they are inconstant structures). Organelles are described as membranous (membrane-limited) and nonmembranous. A.The membranous organelles include: (1) plasma (cell) membrane; (2) rough-surfaced endoplasmic reticulum (rER); (3) smooth-surfaced endoplasmic reticulum (sER); (4) Golgi apparatus; (5) mitochondria; (6) lyzosomes; (7) peroxysomes; B. The nonmembranous organelles include: (1) ribosomes (both those attached to the rER membrane and those free in the cytoplasm) (2) centrioles (and their derivatives); (3) filaments (of various varieties); (4) microtubules. Microtubules and filaments form the cytoskeleton elements. Cell membrane The cell membrane is not visible under the light microscope, because the total thickness of the cell membrane is about 8 to 10 nm. With the electron microscope it appears as if it is formed of three layers: the outer dark layer, the inner dark layer, and the light layer (between the outer and the inner layers). That is why it was called the trilaminar membrane. Sometimes (with low resolution of electron microscope) we can observe only a dark line. The cell membrane is formed of phospholipids, proteins, and carbohydrates. The poshospholipid molecule is composed of two parts: hydrophobic and hydrophilic lipids. The outer dark layer and the 2 inner dark layer of the cell membrane are due to the presence of phospholipids. Large integral proteins are situated between phospholipids. They extend from one side of the cell membrane (the outer dark layer) to the other (the inner dark layer). Large integral proteins perform important functions in cell metabolism, regulation, and integration. They can serve as receptors of enzymes, a pump, or any combination of these functions. Peripheral proteins form a noncontinuous layer in the lipid layers (outer and inner). Cholesterol molecules are present in the cytoplasmic aspect of the cell membrane. Some carbohydrates are attached to large integral proteins and phospholipids. Carbohydrates attached to phospholipids are termed glycolipids; carbohydrates attached to proteins are termed glycoproteins. Glycolipids and glycoproteins form a cell coat or glycocalyx. This outer layer may be very thick or thin, depending on the cell function. Functions of the glycocalyx: 1. It takes part: (a) in cell recognition; (b) in the formation of intercellular adhesion (aids in holding adjacent cells together); (c) in adsorption of molecules to the cell surface. 2. It serves as receptor sites for hormones. Functions of the cell membrane: (1) Passive diffusion of small molecules. The cell membrane can allow dissolved gases, essential ions, and oxygen to pass into the cell. It also allows carbon dioxide and other metabolic wastes to leave the cell; (2) Active transport. In order to pass through the cell membrane, large molecules such as sugar, amino acids, and fatty acids should be combined with some catalysts. This combination requires energy. That is why this transport was termed active. (3) Selective transport. The presence of the receptors on the outer surface of the cell membrane allows it to select and determine which materials can enter the cell and which substances are to leave the cell; (4) Transport of different material by endocytosis is the process of vesicular transport when it involves substances entering the cell. Two forms of endocytosis are recognized: phagocytosis (the Greek for cell eating). For example, the ingestion of bacteria or other cells. pinocytosis (the Greek for cell drinking). For example, the ingestion of bulk fluid. Phagocytosis: Pinocytosis: When a solid particle comes in contact with the The plasma membrane invaginates to form small cell membrane, the membrane gradually pits or caveolae. Gradually these pits will surrounds the particle from all it sides, forming a separate from the cell membrane. They have bag. This bag is pinched off from the cell been referred to as pinocytosis vesicles. membrane and moves inside the cytoplasm. It is called a phagosome. (5) Vesicular transport by exocytosis. Exocytosis is the name given to the process of vesicular transport when it involves substance leaving the cell. For example: the liver produces a very low density lipoprotein (VLDL), which is released to the blood through exocytosic vesicles. VLDL is a component of blood serum that controls the dispersal of serum lipids, a factor important in the development of atherosclerosis. (6) Sodium–potassium pump function. The cell membrane is continually pumping sodium ions to the outside of the cell. As a result the concentration of sodium is higher in the tissue fluid than in the cytoplasm. The concentration of potassium ions is higher in the cytoplasm than in the tissue fluid. The sodium–potassium pump is responsible for the cell membrane polarization. It keeps the cell membrane with a positive charge on the outside and with a negative charge on the inside. Cell membrane modifications The cell membrane is fluid and a dynamic system, not a static structure. It participates in the functional and metabolic activities of the cell. It forms special structures (microvilli and cilia) and junctions. (1) Microvilli.