Department of Histology and Embryology ,
Henan institute of traditional Chinese medicine
December 26, 2004
Prelector,Wanggen Liu
Preface
Histology is a science which study the microstructure under the light microscope(L. M)and the ultra-structure under the electron microscope of the human body, and relationship between the microstructure and function. Embryology is a science which study the development of the human body. The teaching purposes of these subjects are to induce the students who acquire the basic theories and knowledge of these two courses and gain relative basic skill training. By studying, the students should achieve such level: to distinguish the L. M structure of varieties of cells, tissues and main organs, to distinguish the ultra-structure of the main cells and tissues of the body, to know the relationship between the structure and function , to gain a systemic knowledge about the early development of the human embryo and the development of the main organs, to establish a good basis for learning other basic and clinical medical courses.
The basic teaching requirements of Histology and Embryology for medical department of five- year system of traditional Chinese medical college have been given in this outline . The contents in this out-line will be taught by lecture , practice, individual study and so on.
According to the teaching plan of five-year system of traditional Chinese medical college, the total teaching hour is 54. The proportion of lectures to experiments of Histology is 2. 6:1.
The distribution of teaching hours
Chapter Content Lecture practice
Chapter 1 Introduction 1 1. 5
Chapter 2 Epithelial Tissue 2 1. 5
Chapter 3 Connective tissue proper 2 1
Cartilage and bone 2 1
Blood 2 1
Chapter 4 Muscle Tissue 2 1. 5
Chapter 5 Nerve Tissue 3 1. 5
Chapter 6Nerve System(individual study) 0 0
Chapter 7 Circulatory System 2 1. 5
Chapter 8 Immune System 3 0
Chapter 9 Digestive System 5 1. 5
Chapter 10 Respiratory System 2 1. 5
Chapter 11 Urinary System 2 1. 5
Chapter 12 Skin(individual study) 0 0
Chapter 13 Sense Organs (individual study) 0 0
Chapter 14 Endocrine System 3 0
Chapter 15The Male Reproductive System 1 0
Chapter 16 The Female Reproductive System 2 0
Chapter 17 General Embryology (early development) 5 0
Total 39 15
Chapter 1 Introduction
Congratulate all examine smoothly into Henan institute of traditional Chinese medicine. Welcome all to go to my class to learn Histology and Embryology!
Learning objectives
1. Know the research object and purpose of histology and embryology.
2. Know the common research technics of histology and embryology.
3. Know the relationship between the cubic morphology with varieties of
sections.
Teaching contents
1. The research contents and the situation in medicine of Histology and Embryology .
(1)Definition : Histology is a science which study the microstructure of normal human body and the relationship between the structure and function.
(2)Study contents : As you know,our body is composed of a lot of cells,tissues and organs.
Cell:you will learn the structure of cell in biology very detailed.
Tissue: composed of cell group :
Cell: is the structural and functional unit of the body. it is composed of cell membrane、cytoplasm and nucleus
Extracellular matrix (ECM) : is produced by cells
There are four basic tissue : Epithelial tissue,Connective tissue,Muscle tissue and Nervous tissue.
Organs : We will learn the structure of all organs in each system. Each organ consists of several different kinds of tissue.
Histology is a basic and important subject for medical college student. It is also foundamental for further study other subject,such as Pathology、physiology、biochemistry and so on.
2. The common research technics of Histology and Embryology.
There are many methods and techniques used in studing Histology and Embryology. Here,only introduce some basic methods and techniques.
(1). Light microscopy:means to use the L. M to observe the preparations. The most common technique is paraffin sectioning. All the processes will be learn in practical class. The section is usually about 5-10μm. In order to see the structure very clearly,the sections must be stained. The routine staining methods is H. E staining methods. We use two dyes in this method.
Hematoxylin:It is basic dye. It can stain some components in blue. such as nuclear chromatin and ribosome in cytoplasm. Such components are said to be basophilia.
Eosin: It is acid dye. It can stain the protein in red. such as the protein in cytoplasm and extracellular matrix. Such components are said to be acidophilia.
If the components are not easily stained by Hematoxylin and Eosin,such components are said to be neutrophilia.
(2). Electron microscopy:There are two kinds of E. M:Transmission electron microscope(T. E. M) and scanning elctron microscope (S. E. M).
1). Transmission electron microscope: mainly used to study the internal structure of cells and tissues. The working principle in T. E. M is the same as that in L. M. The difference is the section is ultra-thin section,usually it is about 50-80nm. The E. M used a beam of electron in place of visible light that used in L. M. The beam passes through the ultre-thin section ,then is focused on to a fluorescent screen or photographic film by a series electronmagnetic lenses. Using the E. M we can observe the extremely small structure within cells or in extracellular matrix. The resolution of the T. E. M is about 0. 2nm. The ultra-thin section are stained with heavy metal salts,such as lead citrate,in order to in crease structural contrast. The flow of electron can be impeded by those stained tissue. Consequently,if very few electron can penetrate these area to screen. Such area appear dark and are termed electron dense. By contrast,are termed electron lucent.
2). Scanning electrn microscope:This method mainly used to study the surface structure of the cells or tissues. The specimen for examination under the scanning electron microscope is coated evenly with a layer of gold. A finely-focused beam of electrons scans the surface of the specimen. The secondary electrons are emitted from the surface and then collected by a detector. All the signals from many points create an image on a cathode tube,showing the three-dimensional surface structure on screen. The image also can be recorded on photographic film. It has very good depth of focus.
(3). Histochemistry
This method mainly used to study the properties,localizations,quantities of some substance in the cell using histological method and chemical,physical,biochemical,immunological,molecular biological method together.
1). General histochemistry:There are many methods used for detecting different kinds of substances. Here,introduce a method for detecting the polysaccharides. That is Periodic Acid-Schiff(PAS) reaction. In this reaction,periodic acid(HIO4)oxidizes certain hydroxyl groups of the glucose in glycogen to aldehydes ,then,the free aldehydes react with Schiff’s reagent,a colourless basic fuchsin,to produe an insoluble violet-red complex. The positive position(violet-red position)of PAS reaction represent that polysaccharides exist there.
Chemical equation:
Periodic acid(oxidize) Schiff reagent
Polysaccharides(hydroxyl)------↓------aldehyde------↓-----violet-red complex
2). Immunohistochemistry
3)In situ hybridization
3. The relationship between cubic morphology and varieties of sections.
4. The common length unit of microscope , use the international unit system correctly.
Practice contents
Specimen of L. M: H. E stain, AgNo3 strain, histochemistry, PAS reaction, alkaline phosphatase and so on. .
Electron micrograph: The structural pictures of the cell under the transmission electron microscope. The structural pictures under the scanning electron microscope. Freeze fracture, freeze etching pictures.
Demonstration: the manufactory processes of histological sections.
Chapter 2 Epithelial Tissue
Learning objectives
Understand the general features and classification of epithelial tissue.
Understand the structured features and functions of varieties of covering epithelium.
Understand the L. M structure, E. M structured features and functions of microvilli and cilia.
Understand the ultra-structure features and functions of varieties of intercellular conjunctions.
Understand the position, L. M structure, ultra-structure and function of basement membrane.
Know the conception of glandular cells, glandular epithelium and glands, and the morphological classification of exocrine glands.
Teaching contents
1. Outline of epithelial tissue:
1. 1 General structural features:
(1)Epithelial tissue is formed by a large number of regularly and closely arranged epithelial cells.
(2)Polarity:It has a apical free surface,which faces the body or the lumen of an organ and gland,and a basal surface,which faces the underlying connective tissue. There is a basement membrane between the epithelial tissue and the connective tissue.
(3)Avascularity:Most of the epithelial tissue have no blood vessel. The blood vesssels in the connective tissue can provide the nutrition to epithelium by means of diffusion through the basement membrane. There are a lot of small branches of nerve fibers in the epithelium.
(4)The epithelial tissue have many functions:
such as protection,absorption,secretion and excretion.
1. 2 The classification and general functions of epithelium.
According to the function and structure,epithelial tissue can be classified as:
Covering epithelium: protect
Glandular epithelium: secretion
Special epithelium
2. Covering epithelium: Cover the surface or line the cavity of the body. Epithelial cells are arranged in one or more than one layers. According to the number of layers the and shape covering epithelium can be divided into two kinds:
(1)Simple epithelium:
Simple squamous epithelium : endothelium and mesothelium
Simple cuboidal epithelium
Simple columnar epithelium: Goblet cell------mucinogen granule
Pseudostratified ciliated columnar epithelium
(2)Stratified epithelium:
Stratified squamous epithelium:keratinized and non-keratinized
Transitional epithelium
The structure of each kind of epithelium will be learn by yourself after class.
3. The special structures of epithelial cell : In order to adapt their function,The
epithelial cells differentiate some special structure on their free surface,lateral surface and basal surface.
(1). Free surface: There are two special structure on the free surface.
1). Microvillus: It is small,slender,finger-like projection of apical cell surface consisting of cell membrane and cytoplasm. It is about 0. 2μm in diameter. They are too small to be seen clearly under light microscope. They only can be seen clearly under E. M. But in some epithelium,they are numerous and form a visible striated border which can be seen under L. M. Such as in the absorptive cell of the epithelium in small intestine.
Structure:Under E. M,there are many longitudinal microfilament in the microvillus. The basal portion of the microfilament are embedded in and interconnected with terminal web,which lies in the apical cytoplasm just beneath the cell surface.
Function:They can increase the aborptive surface.
2). Cilium: They are also the projections of cell surface. it is about 5-10μm long and 0. 2μm in diameter. They are much thicker and longer than microvillus. They are visible under L. M.
Structure:They also consist of cell membrane and cytoplasm. There are a pair of microtubule in the center of cilium and nine doublet microtubules around the central microtubules. At the base of each cilium,there is a basal body located in the apical cytoplasm just below the cell membrane.
Function:They can remove some small particles from the cell surface. It mainly distribute on the epithelium lining the respiratory tract,such as trachea and bronchus.
(2). Lateral surface:In the lateral surface,There are cell-to-cell adhesions. we call them cell junctions. Those structure only can be seen un der E. M.
1). tight junction:It also be called zonule occludens. They are belt-shaped encircling the apex of the cell. Under the E. M,the tight junction show the fusion of the outer layer in the two plasma membranes . There is no intercellular gap in the fusion portion.
Function:The tight junction can prevent the substance pass through the intercellular space.
2). Intermediate junction:It is also called zonule adherens. It also encircle the cell just beneath the tight junction. There is a intercellular gap of 15-20 nm containing some filamentous material. The cytoplasmic surfaces of inner layers of two cell membranes show a thin layer electron –dense materialassociated with terminal web.
3). Desmosome:It is also called macula adherens. They are small Plate-shaped structure. There is an intercellular space of 20-30 nm be tween twocell membrane. The space is filled with filamentous material. In the center ,there is a dense line termed intermediate line. On the cytoplasmic surface of inner layers of two cell membrane there are dense attachment plaques. 10 nm tonofilaments pass into the attachment plaques and then loop back into the cytoplasm. Desmosome is the firmest junction.
4). Gap junction:It is also called communication junction. There is an intercellular space of only 3 nm. There are many connections between the two cell membranes. Each connection is about 7-9 nm in diameter and is formed by six subunit called connexins arranged around a central channel. The channel is about 2 nm in diameter. The connections in opposing cell membranes are connected to each other. The structure permit directly cell-to-cell interchange.
If there are two or more than two cell junctions,these are called junctional complex.
(3). Basal surface
1). Basement membrane:Basement membrane is a thin membrane between the epithelium and connective tissue.
Structure:Under the E. M,the basement membrane is composed of basal lamina and reticular lamina.
Basal lamina: produced by epithelial cells and about 50-100 nm in thickness.
Reticular lamina: produced by fibrocytes and composed of reticular fiber and ground substance,
2). plasma membrane infolding:They are formed by infolding of basal membrane. There are many mitochondria in cytoplasm around the infoldings. The infoldings increase the basal surface.
3). Hemidesmosome:It is a half of each desmosome in structure occurred on the basal surface. They have the function to fix the epithelial cell onto the basement menbrane.
4. Glandular epithelium: Glandular epithelium and gland
(1). Concept:
Glandular epithelium:It is composed of cells which have the function of secretion and synthesis.
Gland:Gland is an organ which is mainly composed of glandular epithelium.
(2). Classification of gland:According to having duct or not,Gland can be divided into:exocrine gland and endocrine gland.
(3). Exocrine gland :It is composed of secretory portion and duct.
Duct:composed of simple or stratified epithelium. Duct can discharge gland secretion to body surface.
Secretory portion:It is also called acinus. At the end of duct,composed of a layer of glandular cells and a cavity in the center.
According to the nature of secretions,The glandular cells can be divided into: