Kharkov National Medical University Department of Histology, Cytology and Embryology Lecture 1. Introduction. Essential Cytology

Histology – studies the organization of the tissues and organs of the human organism. Cytology – studies the structure and functions of the cell. Embryology – researches embryonic development (formation) of human body.

Cytology

The cell is the smallest structural and functional unit of multicellular organisms. the smallest structural and functional unit of multicellular organisms. Cells form tissues, tissues form organs and systems. Cells form tissues, tissues form organs and systems.

Types of cells in human body

Cells produce matrix:

Methods of investigation

Microscopy – basic method Light microscope: Light microscope: Histological slide: Histological slide:

Electron microscopy

Electron microscopy researches Ultrastructure of cells (organelles) and organisation of intercellular matrix Ultrastructure of cells (organelles) and organisation of intercellular matrix

Light and electron microscopy - are 2 main methods in histology

Another methods: Polarized microscopy (property of tissues: can rotate the angle of the plan of polarized light) Polarized microscopy (property of tissues: can rotate the angle of the plan of polarized light) Faso-contrast microscopy Faso-contrast microscopy

Levels of biological systems Biomolecules Biomolecules membranes organelles membranes organelles CELL CELL

Cell Membrane contents: Phospholipids: Phospholipids: 1 – hydrophilic heads 1 – hydrophilic heads 2 – hydrophobic tails 2 – hydrophobic tails 3 – proteins 3 – proteins 4 – carbohydrates (only outer cell membrane) 4 – carbohydrates (only outer cell membrane)

Lipids may be: Phospholipids – triglycerides (polar) Phospholipids – triglycerides (polar) Cholesterol (non-polar) Cholesterol (non-polar)

Phospholipids : Phosphate group (hydrophilic heads) Phosphate group (hydrophilic heads) Glycerol Glycerol Fatty acids (hydrophobic tails) Fatty acids (hydrophobic tails)

Cholesterol is especially abundant in the plasma membrane of mammalian. Cholesterol is especially abundant in the plasma membrane of mammalian. As much as 30 to 50 percent of the lipids in plant plasma membranes consists of cholesterol As much as 30 to 50 percent of the lipids in plant plasma membranes consists of cholesterol

Proteins may constitute close to 50% of membrane content function : in the membranes 1- channels, 1- channels, 2- pumps, 2- pumps, 3- receptors, 3- receptors, 4- enzymes, 4- enzymes, 5- integrative, 5- integrative, 6- structural 6- structural

Carbohydrates (in glycoproteins) Present in the outer cell membrane Present in the outer cell membrane Role - Receptors Role - Receptors

Outer cell membrane – cytolemma or plasmalemma

Membranes form BARRIER between 2 mediums, Membranes form BARRIER between 2 mediums, regulate exchange and trasport regulate exchange and trasport creates COMPARTMENTS creates COMPARTMENTS in the cell in the cell

Membranes form: Outer cell membrane – cytolemma or plasmalemma Outer cell membrane – cytolemma or plasmalemma Organelles Organelles Vesicles Vesicles Nucleus - nuclear envelope Nucleus - nuclear envelope

Structure of a typical cell 1. Cell membrane 2. Nucleus 3. Cytoplasm

Cell consists of: - Outer cell membrane, - Outer cell membrane, - Cytoplasm and - Cytoplasm and - Nucleus - Nucleus

If cells contact with the neighboring cells, If cells contact with the neighboring cells, outer cell membrane forms cell junctions outer cell membrane forms cell junctions

12 G Where Cells contact -- Cell junction

Types of Cell junction Tight junction Tight junction Gap junction Gap junction Desmosomes Desmosomes

Tight junction Is present between epithelial cells Is present between epithelial cells two layers of glycocalyx are fused. Structure: two layers of glycocalyx are fused. Function: prevents the movement of molecules into the intercellular spaces Function: prevents the movement of molecules into the intercellular spaces

G

Gap junction Channels between cells Channels between cells allow for direct communication between cells through diffusion allow for direct communication between cells through diffusion numerous in muscle tissue numerous in muscle tissue

Gap junction Consists of six connexin proteins, interacting to form a cylinder with a pore in the centre - connexon. Consists of six connexin proteins, interacting to form a cylinder with a pore in the centre - connexon. This protrudes across the cell membrane, and when two adjacent cell connexons interact, they form the gap junction channel This protrudes across the cell membrane, and when two adjacent cell connexons interact, they form the gap junction channel

Desmosomes - Provide cell attachment Provide cell attachment

dense layer of protein present on the inner (cytoplasmic) surface of the cell membrane (= dense plaque). dense layer of protein present on the inner (cytoplasmic) surface of the cell membrane (= dense plaque). Intermediate filaments composed of keratin or desmin are attached to dense plaque. Intermediate filaments composed of keratin or desmin are attached to dense plaque. Small gap between two membranes is rich in glycoprotein Cadherin, which looks like a thin filaments. Small gap between two membranes is rich in glycoprotein Cadherin, which looks like a thin filaments.

Inside the cell : Cytoplasm and nucleus Cytoplasm and nucleus

Inside the cell … Cytoplasm consists of: Matrix (hialoplasm, cytozol) Matrix (hialoplasm, cytozol) Organelles Organelles Inclusions Inclusions

Inclusions - granules with secretions, pigment granules, lipid and glycogen droplets granules with secretions, pigment granules, lipid and glycogen droplets

Organelles: classification by structure Membranous Membranous Non-membranous Non-membranous

Organelles: classification by function General (are present in every cell, perform general function) General (are present in every cell, perform general function) =Mitochondrion =Mitochondrion Special (in specialized cell, perform special function) Special (in specialized cell, perform special function) = Myofibril = Myofibril = Neurofibril = Neurofibril

Rough endoplasmic reticulum Membranes form a network of sac-like structures called cisternae. Membranes form a network of sac-like structures called cisternae. ribosomes lie on the outer surface; ribosomes lie on the outer surface; Function - synthesis of proteins Function - synthesis of proteins

Smooth endoplasmic reticulum, SER

Membranes form tubules without ribosomes. Membranes form tubules without ribosomes.Function: 1. synthesis of lipids. 1. synthesis of lipids. 2. metabolism of carbohydrates 2. metabolism of carbohydrates 3. drug detoxification (in liver cells). 3. drug detoxification (in liver cells). 4 Storage of Ca-ions (only in muscle cell) 4 Storage of Ca-ions (only in muscle cell)

Golgi complex (or apparatus) = a pack of sacs. = a pack of sacs.

Golgi complex is connected with endoplasmic reticulum Golgi complex is connected with endoplasmic reticulum

Golgi apparatus functions: 1. formation of compound molecules – glycoproteins, lipoproteins. 1. formation of compound molecules – glycoproteins, lipoproteins. (which has begun in endoplasmic reticulum and is accomplished in the Golgi complex). (which has begun in endoplasmic reticulum and is accomplished in the Golgi complex).

Golgi apparatus Functions. 2. production of lysosomes and secretory vesicles. 2. production of lysosomes and secretory vesicles.

Mitochondrion - contains outer and inner membranes - contains outer and inner membranes --Folds of inner membrane – cristae --Folds of inner membrane – cristae --- Inside M. lies matryx --- Inside M. lies matryx

Mitochondrion Produces ATP molecules (energy) by Krebs cycle Produces ATP molecules (energy) by Krebs cycle

Lysosome Lysosomes are round vesicles that contain acid hydrolase enzymes Lysosomes are round vesicles that contain acid hydrolase enzymes These enzymes break down waste materials and cellular debris and digest the materials within phagosomes. These enzymes break down waste materials and cellular debris and digest the materials within phagosomes.

Lysosome Cycle lysosomes are formed in the Golgi complex lysosomes are formed in the Golgi complex The nearly produced lysosome is primary lysosome The nearly produced lysosome is primary lysosome

Lysosome Cycle primary lysosome fuses with the phagosome -- secondary lysosome or phagolysosome primary lysosome fuses with the phagosome -- secondary lysosome or phagolysosome part of undigesting material may remain within the cell as residual bodies. part of undigesting material may remain within the cell as residual bodies.

Fagocytosis

Non-membranous organelles: Microfilaments Microfilaments Microtubules Microtubules Centrioles (Cell Center) Centrioles (Cell Center) Ribosomes Ribosomes

The cytoskeleton - is made up of three kinds of protein filaments: - is made up of three kinds of protein filaments: Actin filaments (also called microfilaments) Actin filaments (also called microfilaments) Intermediate filaments Intermediate filaments Microtubules Microtubules

Microfilaments, Microtubules form “Skeleton” of the cell

Β-tubulin actin

Cell center Consists of 2 centrioles Centriole = 9 x 3 = 27 microtubules; function - formation of mitotic spindle

Cell center

Special organelles Myofibrils Myofibrils Cilia, microvilli Cilia, microvilli

Nucleus Eukaryotes have nucleus Eukaryotes have nucleus

Nucleus consists of: Nucleolemma - nuclear envelope Nucleolemma - nuclear envelope Nucleoplasm Nucleoplasm Nucleolus Nucleolus Chromatin, chromosomes Chromatin, chromosomes

Nuclear envelope - Consists of two membranes: - Consists of two membranes: outer and inner outer and inner

In the nuclear envelope there are gaps, called nuclear pores there are gaps, called nuclear pores (transport some substances from nucleus into cytoplasm) (transport some substances from nucleus into cytoplasm)

Nuclear pore structure

Nucleolus Nucleolus is the site of active synthesis of ribosomal RNA and formation of ribosomes. Nucleolus is the site of active synthesis of ribosomal RNA and formation of ribosomes.

Nucleolus Nucleolus is the site with very amplificated molecule of DNA. Nucleolus is the site with very amplificated molecule of DNA. It is the site of active synthesis of ribosomal RNA. It is the site of active synthesis of ribosomal RNA.

Nucleolus Forms ribosomal RNA and ribosomal subunits, Forms ribosomal RNA and ribosomal subunits,

Chromosome = DNA molecules + proteins ( histones) 46 Chromosomes 46 Chromosomes

Chromatin is the combination of DNA and proteins that make up the contents of the nucleus of a cell. is the combination of DNA and proteins that make up the contents of the nucleus of a cell. The primary functions of chromatin are 1) to package DNA into a smaller volume to fit in the cell, 2) to strengthen the DNA to allow mitosis, 3) to prevent DNA damage, and 4) to control gene expression and DNA replication The primary functions of chromatin are 1) to package DNA into a smaller volume to fit in the cell, 2) to strengthen the DNA to allow mitosis, 3) to prevent DNA damage, and 4) to control gene expression and DNA replication

Chromatin = DNA in non- dividing cells. 2 types: 2 types: 1. heterochromatin (non-active) - very tightly packed fibrils. 1. heterochromatin (non-active) - very tightly packed fibrils. 2.euchromatin - active – less condensed chromatin fibrils loops 2.euchromatin - active – less condensed chromatin fibrils loops

Euchromatin predominates in metabolically active nuclei, Euchromatin predominates in metabolically active nuclei, Heterochromatin predominates in metabolically inactive nuclei Heterochromatin predominates in metabolically inactive nuclei

Chromosome is an organized structure of DNA and protein found in cells.

Cell Cycle The life of a somatic cell is a cyclic process The life of a somatic cell is a cyclic process It is called cell cycle It is called cell cycle consists of two periods: interphase and mitosis. consists of two periods: interphase and mitosis.

Interphase Interphase is a period between two divisions of the cell. Consists of 3 phases - G 1, S, G 2

In G1 phase: cell grows, performs its routine functions. cell grows, performs its routine functions.

In G 1 phase Nondividing cells complete period G 1 by growing old and death of the cell Nondividing cells complete period G 1 by growing old and death of the cell Dividing cell – prepares for the next phase Dividing cell – prepares for the next phase

S- phase = synthesis phase DNA molecules are duplicated DNA molecules are duplicated At the beginning of this phase the chromosome number is 2N and at the end each chromosome consists of two DNA molecules or two chromatids, the chromosome number is 4N.

G 2 phase In this phase synthesis of proteins which are required for cell division takes place. In this phase synthesis of proteins which are required for cell division takes place. After phase G 2 mitosis always begins After phase G 2 mitosis always begins

G 0 phase cell can leave the cycle and enter the so-called G 0 phase (outside the cycle). They are reserve or stem cell. cell can leave the cycle and enter the so-called G 0 phase (outside the cycle). They are reserve or stem cell.

Mitosis is the process of somatic cells division. Mitosis consists of four phases: prophase,metaphase,anaphase,telophase.

Prophase Chromosomes become recognisable. Chromosomes become recognisable. the nuclear membrane breaks down and the nucleoli disappear the nuclear membrane breaks down and the nucleoli disappear

Two centrioles separate and move to opposite poles of the cell. Two centrioles separate and move to opposite poles of the cell. microtubules pass from one centriole to other and form a spindle of division. microtubules pass from one centriole to other and form a spindle of division.

Metaphase - chromosomes move to a position midway between the two centrioles (the equator of the cell) and form the equatorial plate - chromosomes move to a position midway between the two centrioles (the equator of the cell) and form the equatorial plate

anaphase - the chromatids separate and move to opposite poles of the cell - the chromatids separate and move to opposite poles of the cell At the end of anaphase chromatids are called chromosomes. At the end of anaphase chromatids are called chromosomes.

Telophase two daughter nuclei are formed two daughter nuclei are formed chromosomes become indistinct. chromosomes become indistinct. Nucleoli reappear. Nucleoli reappear.