Histology and Cytology PDF

2 Histology and cytology Definition of Histology: “Histo” comes from Greek which means “tissue” “Ology” comes from Greek which means “branch of knowledge” Definition of cytology: “Cyto” comes from Greek which means “cell” Histology requires the use of “Microsco...

2 Histology and cytology Definition of Histology: “Histo” comes from Greek which means “tissue” “Ology” comes from Greek which means “branch of knowledge” Definition of cytology: “Cyto” comes from Greek which means “cell” Histology requires the use of “Microscopes” to view the structures under increasing magnifications. Types of microscopes Light microscope Electron microscope Parts of light microscope  3 Light microscope (compound) Electron microscope Small Large and non-portable Relatively inexpensive Expensive Does not need a lot of training Training is required Colored image Black and white image Specimen can be alive and unharmed Specimen must be dead Lower resolving power Greater resolution Lower magnification Greater magnification Skeletal muscle by light microscope Skeletal muscle by electron microscope  4 Resolution and magnification Resolution Magnification The ability of microscope to show two The ability of microscope to magnify points very close to each other as two objects separate points Magnification = Power of ocular x objective lens For light microscope is 0.2 µm. For light microscope: nearly 1500-2000 For electron microscope is 0.2 nm For electron microscope: nearly 500000 Methods of studying cells and tissues Microtechniques: Techniques used for tissue preparation for microscopic studies. For light microscopy: 1. Paraffin technique. 2. Frozen sections. 1. Paraffin technique The paraffin technique is the most commonly used. Once the sections are prepared, they are usually stained, to distinguish the components of the tissue as the optical density of the different components is very similar. Steps as follow: 1. Fixation: Agent: Solution of formaldehyde, at neutral pH is used to fix tissues and organs. Aims of fixation: Prevent autolysis by stabilizing lysosomes of the cells preserving tissue structure. Binds to and cross-links some proteins which hardens the tissue to facilitate cutting. Fixation kills bacteria thus prevent putrefaction. It enhances the affinity to tissue staining.  5 2. Washing in running tap water. 3. Dehydration: First, the tissue has to be dehydrated by replacing water in the sample with alcohol gradually to prevent tissue shrinkage. This is achieved by passing the tissue through increasing concentrations of ethyl alcohol (from 0 to 100%). Finally, water has been replaced by 100% alcohol. 4. Clearing: the alcohol is replaced with xylene, which is a paraffin solvent. Xylene also makes the tissue transparent. 5. Impregnation and Embedding: using hot oven, the tissue is placed in warm paraffin wax and the melted wax melting point is (55-60 C) fills the spaces that used to have water in them. 6. Sectioning: the tissue is trimmed and mounted on a cutting device called a microtome (shown in the picture). Serial thin sections (5-7 µm thickness) are cut, which can be mounted on a microscope slide. 7. Mounting: It is then mounted on a clean glass slide. 8. Staining: unfortunately, most staining solutions are aqueous, so to stain the sections, the wax has to be dissolved and replaced with water (rehydration). The sections are passed through xylene, and then decreasing strengths of alcohol (100% to and finally water). Once stained, the section is then dehydrated once again, and placed in xylene and a coverslip is placed to protect the sample. Hematoxylin and eosin (H&E) A universally used for routine histological examination of tissue sections. Hematoxylin Eosin Basic dye that stains acidic components Acidic dye that stains basic components of the cell (nucleus) giving blue color of the cell (cytoplasm) giving reddish (basophilia) pink color (Acidophilia)  6 2. Freezing technique Tissues are frozen rapidly in liquid nitrogen, and then cut in a refrigerated cabinet (a cryostat) with a cold knife, then stained and observed in the microscope. This procedure is faster (takes only minutes) and can preserve tissue details that may be lost by the paraffin technique. Sections are 5 - 10 µm thick. Used for intra-operative consultation (needed in tumor surgery) as it allows rapid decision and report. The cell It is the structural and functional unit of all living tissues. Size: In human there is wide variation cell size. Shape: Varies according to the function of cells as in RBCs, WBCs, and nerve cell  7 Structure of the cell 1. Nucleus: The genetic control center of a eukaryotic cell 2. Cytoplasm: consists of cytosol, organelles, and inclusions. Cytosol: It is a jelly-like substance composed mainly of water and found between the cell membrane and nucleus. The cytoplasm makes up most of the "body" of a cell and is constantly streaming. Organelles: 1. Membranous organelles: Cell membrane, Mitochondria, Endoplasmic Reticulum, Golgi apparatus, Lysosome, Peroxisome and Vesicle. 2. Non membranous organelles: Ribosome, microtubules, and filament. Inclusions: Non-essential for vitality of the cells. Structure of the Cell Cytoplasm Nucleus Organelles Inclusions (Essential-for cell vitality) (Not essential-for cell vitality) A. Stored food Membranous Non-Membranous B. Pigments C. Crystals 1. Cell membrane 1. Ribosomes 2. Mitochondria 2. Microtubules 3. Endoplasmic reticulum 3. Filaments 4. Golgi apparatus 5. Lysosomes 6. Peroxisomes 7. Coated vesicles 1. Cell membrane  8 Definition: A living membrane forming the outermost cover of the cytoplasm (plasma membrane). It surrounds the membranous organelles (internal membranes) Structure: LM: Cannot be seen because it is very thin (8-10 nm) EM: the average cell membrane is seen to be about 7.5 nm thick. It consists of two densely stained layers separated by a lighter zone, thus creating a trilaminar appearance. Biochemical structure: Cell membranes are made up predominantly of lipids, Proteins and carbohydrates are also present. A. Lipids: 1. Phospholipids are the main constituents of cell membranes. Each phospholipid molecule consists of an enlarged head in which the phosphate portion is located; and of two thin tails. Arrangement of phospholipids in the cell membrane explains the Trilamellar EM structure The head end is the polar end, hydrophilic (soluble in water) and is directed peripherally forming the dark staining parts of the membrane seen by EM. The tail end is the non-polar, hydrophobic, and directed to the center forming the light staining intermediate zone  9 Outer layer Head Head Phospholipids Inner layer Outer layer Tail Cholesterol Tails Inner layer Head 2. Cholesterol provides stability to the membrane. 3. Glycolipids are present only over the outer surface of cell membranes. B. Proteins: Carbohydrates: Present at the external surface of the membrane. They are attached either to the proteins (forming glycoproteins) or to the lipids (forming glycolipids). This carbohydrate layer forms the cell coat or glycocalyx. Glycoprotein Glycolipid Cell coat Lipid bilayers Cholesterol Protein  10 The cell coats It is a layer of glycoproteins and glycolipids which are present on the external surface of cell membrane Functions of cell coat: Protection of the cell. It contains special adhesion molecules which enable the cell to adhere to specific types of cells, or to specific extracellular molecules. It contains antigens. As in erythrocytes, the glycocalyx contains blood group antigens. Most molecules in the glycocalyx are negatively charged causing adjoining cells to repel one another. This force of repulsion maintains the 20 nm interval between cells. Function of cell membrane: 1. Passive Transport Simple Diffusion: water, oxygen and other molecules move down a concentration gradient (from high to low concentration). Facilitation Diffusion assisted by proteins (channel or carrier) Osmosis - diffusion of water. 2. Active Transport: occurs against the concentration gradient, and requires energy (ATP): Sodium-Potassium Pump: pumps out 3 sodium ions for every 2 potassium's taken in against gradient 3. Bulk transport: Endocytosis: taking substances into the cell (pinocytosis for water, phagocytosis for solids). The cell membrane first surrounds the molecule, invaginates and then separates to form an endocytic vesicle. Exocytosis: pushing substances out of the cell, such as the removal of waste molecules produced within the cytoplasm (e.g., secretions) may be enclosed in membranes to form vesicles that approach the cell membrane and fuse with its internal surface. The vesicle then ruptures releasing molecule to the exterior. 4. Support the cell and help maintain its shape.  11 2. Mitochondria (The powerhouse of the cell) Definition: membranous organelle, concerned with energy production. Their number varies from one thousand in liver cells (active) to few mitochondria in fat cells (inactive). L.M: Can be visualized only by using special stains. EM: Each mitochondrion has two membranes: 1- Outer smooth membrane. 2- Inner membrane which is folded into cristae. These cristae increase the surface area and possess the elementary particles, which carry the respiratory chain enzymes responsible for energy production. -The narrow space between the inner and outer membrane called the intermembrane space. The interior of the mitochondria is called the intercristae space (matrix space). This space is filled with a matrix rich in protein and contains mitochondrial RNA& circular DNA and dense granules rich in Ca2+. N.B: New mitochondria originate from preexisting mitochondria by growth and subsequent division (binary fission) of the organelle itself. Function: 1. The primary function of mitochondria is to convert organic materials into cellular energy in the form of ATP. 2. Mitochondria help the cells to maintain proper concentration of calcium ions within the compartments of the cell. 3. The mitochondria also play important role in the process of apoptosis. Mitochondrial Disease: Dysfunction in the mitochondria fails to produce energy that is needed for the sustainment of life and growth of an organism. The mitochondrial disease causes most of the damage to the cells of brain, heart, liver, muscles, and kidney. The symptoms may be loss of motor  12 control, muscle weakness and pain, gastro-intestinal disorders, poor growth, cardiac disease, and liver disease. Membranous organelles (cell factories and transport organelles): Rough Endoplasmic reticulum (rER) Smooth Endoplasmic reticulum (sER) Golgi apparatus Lysosomes Summary 3. Endoplasmic reticulum (rER) Rough endoplasmic reticulum Smooth endoplasmic reticulum Structure :Tubules + ribosomes Tubules Acidophilic H&E: Basophilic Acidophilic EM: Tubules + Ribosomes Tubules Function: Protein metabolism Lipid, Ca, HCl, drug metabolism  13 A. Rough Endoplasmic Reticulum (rER) Definition: RER is a series of connected parallel flattened tubules (cisternae) with ribosomes attached to its surface. Its density is higher near the nucleus and the Golgi apparatus. LM: It is basophilic due to the presence of ribosomes on its outer surface. EM: The RER appears as communicating flattened tubules called cisternae, covered with ribosomes. Function: It plays a central role in the synthesis of proteins. Proteins travel as transfer vesicles to Golgi apparatus. Manufacture of lysosomal enzymes. B. Smooth Endoplasmic Reticulum (rER) Definition: The SER appears as branching anastomosing tubules or flattened vesicles with smooth wall. There are no ribosomes on the surface. It is more tubular in shape than RER. Another type of endoplasmic reticulum is Sarcoplasmic Reticulum, which is a type of specialized SER that can be found in muscles. L.M: Cells with extensive SER may exhibit cytoplasmic acidophilia. EM: The SER appears as branching anastomosing tubules or flattened vesicles with smooth wall. There are no ribosomes on the surface. Functions: Lipid synthesis: Especially in the steroid-secreting cells such as cells of adrenal cortex. Glycogen metabolism: Enzymes involved in regulating glycogen metabolism are associated with the SER membrane for example in the liver cells. Regulation of mineral metabolism e.g. HCL production in the stomach. Calcium storage: in the skeletal and cardiac muscle fibers to control muscle contraction. Drug detoxification: Due to the presence cytochrome P450 enzyme in the SER membrane especially in the liver cells.  14 Medical application: Jaundice is caused by accumulation of bilirubin which are normally metabolized by SER enzymes in cells of the liver and excreted as bile. A frequent cause of jaundice in newborn infants is an underdeveloped state of SER in liver cells. 4. Golgi complex (Apparatus) Definition It is a membranous organelle that processes, packages, and sorts of macromolecules such as proteins and lipids after their synthesis. L.M It could be visualized only by using special stains. In the deeply basophilic cytoplasm of the protein secreting cells as plasma cell, its position appears as non-stained area called Negative Golgi Image. E.M The Golgi complex is formed of: 1- Golgi stack: It is composed of a variable number, typically 3-6, of flattened sacs called cisternae. Each stack has a convex immature surface facing the nucleus called (Cis Face) and a concave mature surface towards the cell membrane called (Trans Face). 2-Transfer (microvesicles): They derived from rough endoplasmic reticulum and fuse with the convex surface. 3- Secretory (macrovesicles): They are formed by budding from the mature surface of Golgi. It remains within the cytoplasm as lysosomes or exocytosed out-side the cell. Function: 1. Share in the formation of lysosomes. 2. Modifies the proteins by the addition of carbohydrates and phosphate to proteins 3. Keeps cell membrane and cell coat intact through the process of exocytosis.  15 5. Lysosomes Definition They are a membrane bound spherical vesicles containing hydrolytic enzymes, concerned as the rubbish disposal unit of the cell. Lysosomes are abundant in cells with phagocytic activity such as macrophage. LM: They may be demonstrated in cell sections by immunohistochemical techniques. EM: Primary lysosomes appear spherical homogenous electron-dense vesicles. Secondary lysosomes appear spherical heterogenous electron-dense vesicles as they contain digested elements. Formation of lysosomes Lysosomal enzymes are synthesized and segregated in the RER. Then they transferred to the Golgi complex as transfer vesicles. In the Golgi complex enzymes are modified and packed as lysosomes. Types of lysosomes: 1. Primary Lysosomes: Lysosomes that have not entered into a digestive process appear as homogenous vesicle. 2. Secondary Lysosomes: Lysosomes that have entered into a digestive process include different subtypes: a) Heterophagosome: result when the secondary lysosome fuse with solid particles (phagosome). b) Multi-vesicular body: result when the secondary lysosome fuse with pinocytotic vesicle. c) Autophagosome: if the digested material is one of cytoplasmic organelles. Fate of the digested material 1. After digestion, nutrients diffuse through the lysosomal membrane and enter the cytoplasm for reuse.  16 2. Indigestible compounds are retained within the vacuoles, which are now called residual bodies extruded outside the cell by exocytosis. Functions of lysosome: 1. Release enzymes outside the cell for destroying material around the cell such as in osteoclast. 2. Digestion of material from inside the cell such as old mitochondria. 3. Digestion of material engulfed from outside the cell example bacteria. 4. Digestion of completely breakdown cells that have died (autolysis). N.B: In some long-lived cells (e.g. neurons, heart muscle), large quantities of residual bodies accumulate and are referred to as lipofuscin, or age pigment. In some diseases, a specific lysosomal enzyme is absent or inactive, and certain molecules (e.g. glycogen) are not digested. As a result, these substances accumulate in the cells, interfering with their normal functions. 6. Peroxisomes (microbodies) Definition: Small (0.2-1.0 μm), membrane-bound organelles that contain oxidative enzymes. Functions:  17 1- Peroxisomes oxidize specific organic substrates producing hydrogen peroxide (H2O2) that is very damaging to the cell. 2- H2O2 is eliminated by the enzyme catalase, which is present in peroxisomes. 3- Catalase degrades several toxic molecules and drugs, particularly in liver and kidney peroxisomes. 4- Peroxisomes contain enzymes involved in lipid metabolism. Non membranous organelles Ribosomes Definition: Small rounded or oval cytoplasmic non-membranous organelles, formed of ribonucleoprotein (RNA + Protein). They are responsible for protein synthesis. Free ribosomes Site of their formation: Polysomes They are formed in the nucleolus. Attached They are present in 3 forms: Free in the cytoplasm. Attached to the rough endoplasmic reticulum. Polysomes or polyribosomes; free or attached ribosomes found in clusters connected by a strand of messenger RNA. LM: Too small to be seen but they are responsible for basophilia of the cytoplasm EM: Formed of two subunits: Small subunit Large subunit which is double the size of the small one. It contains a channel through which the newly synthesized polypeptide chain exits. Function: Protein synthesis. 1. Free ribosomes synthesize proteins for cell own needs. 2. Attached ribosomes synthesize proteins that will be secreted by the cell. Centrioles  18 Definition: They are a pair of cylindrical rods oriented at a right angle to each other near the center of the cells that can divide. EM: Each centriole appears as a hollow cylinder; its wall is formed of 27 microtubules. The 27 microtubules are arranged in the form of nine bundles of microtubules called triplets each is composed of three microtubules. Functions of centrioles: 1. During cell division, centrioles duplicate, and each pair move to the opposite poles of the cell, where they form the mitotic spindle needed for chromosomal separation. 2. Formation of basal bodies of the cilia. Cytoskeleton Definition: Forms the skeleton of the cell cytoplasm. Formed of: 1. Microtubules 2. Microfilaments 3. Intermediate filaments. Functions of the cytoskeleton: 1. Cell shaping 2. Cell motility 3. Cell division. 4. Organelles anchoring and organization. 5. Intracellular movement of vesicles: Endocytosis, exocytosis, and phagocytosis 1. Microtubules: They are present nearly in all cells and form of a protein called tubulin. LM: Microtubules are too small to be seen EM: They are hollow, cylindrical tubules of about 25 nm in diameter and of variable length. Function: 1. They form the skeleton of the cell. 2. From which centrioles, the basal body of cilia and flagellum are formed. 3. They form the mitotic spindle during mitosis to guide the movement of chromosomes. 2. Microfilaments  19 Actin filaments, they are thin thread like structures about 6-7 nm in diameter and of variable length, they are present in muscle cells. Functions of microfilaments: They are supportive elements in cells, responsible for muscle contraction, amoeboid movement, and cell motility. 3. Intermediate filaments: Long unbranched filaments, their average diameter 10 nm. They are of different subtypes: Keratin, in epidermis of the skin. Vimentin, in fibroblasts. Desmin, in smooth muscle. N.B Diameter of intermediate filament is intermediate between actin thin filaments and myosin thick filaments. Cytoplasmic inclusions Definition: They are non-living temporary components of the cytoplasm produced as a result of cell activities. Organelles Inclusions Metabolically active Inert Permanent Temporary Essential non-essential for vitality Like body organs Storage food e.g. mitochondria e.g. glycogen Types of inclusions are: 1-Stored food e.g. carbohydrates and lipids. 2-Colored pigments. 3-Crystals. A. Stored food: 1. Carbohydrates: are stored in cells in the form of glycogen for energy reserve, especially in liver and muscle cells.  20 LM: Glycogen can be stained by PAS or Best’s carmine method. EM: Glycogen particles appeared as electron dense particles. Clinical application: Glycogen storage disorders: The inability to degrade glycogen leads to the accumulation of glycogen in the cells. lipids: It can be demonstrated using special methods such as Sudan III, Sudan black, and osmium tetroxide LM: H & E stain: Adipocytes (fat cells) appears It can be demonstrated using special methods such as Sudan III, Sudan black and like a signet ring appearance. The cell They are stored in the cytoplasm of some cells mainly in fat cells as droplets. consists of a large lipid globule in the cytoplasm and the nucleus of the cell is pushed out to the periphery of the cell. B. Pigments: -EM: fat droplets appear round and black. Pigmentation means the coloration of certain tissues which may induced by endogenous or exogenous pigment. Endogenous pigments: are formed by cells and include: 1. Hemoglobin: the most important pigment in the body. It is formed in the RBCs. osmium tetroxide. 2. Melanin pigment: responsible for coloration of skin, hair, and iris. It is formed by melanocytes. -LM: 3. Lipofuscin pigment: which accumulated as residual bodies in cells of nerve, heart, and liver. Exogenous pigments: It is the pigment that reaches the cell from outside. There are many types: Carotene pigment: Presents in some vegetables such as orange pigment of carrots and this can color fats in cells as it is lipid soluble. Carbon particles: Present in tobacco smoke, can reach lung tissue in heavy smokers where it was phagocytosed by dust cells.  21 Tattoo marks: When vital stains (i.e., trypan blue) introduced by special needles into the skin they produce permanent coloration. C-Crystals: Crystals may be a product of protein metabolism that accumulate in the cell in high concentrations e.g. uric acid crystals in gout disease Gout is a kind of arthritis caused by deposition of uric acid crystals in the joints. This leads to attacks of painful arthritis, kidney stones, kidney failure. Nucleus Definition: It is membrane-bounded organelle found in eukaryotic cells. It is the control center of the cell. It contains the genome, the cell´s database, encoded in DNA. Most cells have a single nucleus, though some have none (i.e., red blood cells), binucleated (i.e., liver cells) and some have several (i.e., skeletal muscle). Functions: It stores the hereditary material DNA. It Coordinates the cell´s activities which includes growth, metabolism, protein synthesis, and reproduction (cell division). It controls gene expression and mediates the replication of DNA during the cell cycle. Structure: 1. Nuclear membrane (envelop) 2. Nucleolus 3. Nucleoplasm 4. Chromatin 1. Nuclear membrane (envelop) A double membrane that encloses the nucleus and separates it from the rest of the cell. It consists of 2 parallel membranes, separated by a narrow space (perinuclear space), and perforated with pores. A. The outer membrane faces cytoplasm and is rough, continuous with RER. B. The inner membrane is fibrillar due to its attached peripheral chromatin.  22 The two membranes fuse at intervals forming openings (9-11 nm) called nuclear pores (3000-4000 per nucleus), closed by a thin diaphragm. Nuclear pore complex consists of two protein rings each is formed of 8 protein units. From the outer ring, long filaments arise and extend to cytoplasm. From the inner ring, filaments arise and form a basket like structure. Functions of the nuclear membrane: The nuclear envelope contains pores which control the movement of substances in and out of the nucleus. RNA is selectively transported into the cytoplasm, and proteins are selectively transported into the nucleus. 2. Nucleolus Definition: non membranous spherical basophilic bodies found inside the nucleus. These are the sites at which ribosomes are assembled. Nucleoli are most prominent in cells that are synthesizing large amounts of protein. EM: 1. Light area: matrix. 2. Dark area: consists of 3 parts: Nucleolar organizer region consists of DNA molecule in the center that directs the formation of rRNA. Pars fibrosa: filaments of newly formed rRNA surrounding the nucleolar organizer region. Pars granulosa: accumulation of newly formed ribosomal subunits. Functions: DNA in the center direct formation of rRNA that passes to pars fibrosa then to granulosa where then tightly packed and combine with protein forming ribonucleoprotein→ nuclear sap → nuclear pore→ cytoplasm. N.B. tRNA & mRNA are formed in nucleus. 3. Nucleoplasm Highly viscous liquid that contains continuous fibrillary structure (nucleoskeleton) that reinforce nuclear membrane, pore complexes, and hold heterochromatin to inner nuclear membrane. It acts as a media for movement of mRNA, tRNA and rRNA toward nuclear pores.  23 4. Chromatin Combination of DNA, histones and other proteins that make up chromosomes. LM: appear as basophilic granules and threads. EM: There are two types: A. Euchromatin: less compact, lightly stained, contain genes that are frequently expressed by the cell. B. Heterochromatin: more compact form, darkly stained contains DNA that is infrequently expressed. Types of heterochromatin 1. Peripheral: Present in the inner surface of nuclear membrane. 2. Nucleolus associated chromatin(NAC) 3. Chromatin Island: present between nucleolus and nuclear membrane. Functions of chromatin: 1. Stores genetic information. 2. Direct formation of protein inside the cell by formation of the 3 types of RNA. Chromosomes DNA packaging into thread-like structure is called “chromosomes.” Each chromosome is formed of single DNA molecule tightly coiled several times around a histone protein and other proteins. Structure of chromosome  24 At Metaphase stage of cell division, each chromosome appears to be longitudinally divided into two identical parts, each of which is known a 'Chromatid’ (chromosomes are not visible in interphase). Each chromatid has short (p) arm and long (q) arm. Centromere is the region where the two sister chromatids of a chromosome appeared to be held together. Kinetochores are the attachment point for spindle fibers which helps to pull apart the sister chromatids during cell division. kinetochore The two ends of a chromosomes are known as ‘Telomeres.’ Telomere contains many repeats of short identical DNA sequence. - The sequence is (TTAGGG). - It preserves chromosomes. - It is kept long and healthy by telomerase enzyme. Number of chromosomes Chromosomes have specific number in each species e.g. Humans have 46 chromosomes while dog has 78 & fruit fly has 8 chromosomes. In human, each somatic cell contains 23 pairs of chromosomes, for a total of 46, 22 of these pairs called autosomes, look the same in both males and females. The 23rd pair, the sex chromosome, differs between males and females. Females have 2 copies of the X chromosome, while males have one X and one Y chromosome. Haploid and diploid number of chromosomes Haploid Diploid One set of chromosomes Two sets of chromosomes In human, number (n)= 23 In human, 2n = 46  25 In human, gametes (sperm and ova) are In human, all body cells (other than haploid gametes) are diploid Types of chromosomes according to position of centromere Metacentric: centromere in the center→2 equal arms. Sub metacentric: the centromere is slightly offset from the center→ 2 unequal arms. Acrocentric: centromere is severely offset from the center→ very short and very long arms. Telocentric: centromere is at the end→ long arms only, not in human Karyotyping: Karyotype is a complete set of metaphase chromosomes arranged in pairs, on the basis of size, centromere position and shape. In a karyotype, chromosomes are arranged and numbered by size from largest to smallest. Any nucleus can be used to make karyotype ( as Lymphocytes or skin cells). Sampling cells before birth (Amniocentesis, Chorionic villus sampling) could be used for karyotyping.  26 Information Obtained from a Karyotype Number of chromosomes. Sex chromosome content. Presence or absence of individual chromosomes. Nature and extent of large chromosomal abnormalities as Down syndrome (trisomy 21) and Turner syndrome (45 xo) as shown in figures below.