Kharkov National Medical University Department of Histology cytology

Kharkov National Medical University Department of Histology, cytology and embryology

HISTOLOGY studies microscopic structure and function of the human organism

is the structural and functional unit of the organism

Structure of a typical cell 1. Cell membrane 2. Nucleus 3. Cytoplasm cytosol non-membranous organelles

Biological membrane Biological Membrane is a structural unit of a cell in the cell membrane, nucleus and some organelles

Cell membrane (plasmalemma). Outer is glycocalyx

Non-membranous Organelles u 1. Cytoskeleton is the system of microtubules

2 centrioles – consist of 9 triplets of microtubules. Formation of mitotic spindle 2. Cell center

3. Ribosomes two subunits synthesize proteins; Fixed on RER, or free ribosomes

Membranous Organelles

1. Mitochondrion (two membranes) synthesis of energy - ATP

2. Endoplasmic reticulum (net of membranes) smooth (SER) & rough (RER) RER contains ribosomes SER Function: Synthesis Storage Transport SER of lipids and carbohydrates RER of proteins

3. Golgi Apparatus Packaging of proteins, formation of lysosomes, secretion, formation of compound molecules – glycoproteins, lipoproteins

4. Lysosome is digestive apparatus, contains enzymes (autolysis)

Intercellular Junctions 1) Gap Junction has channel proteins

2) Tight Junctions Interlocking proteins

3) Desmosomes STRONG BOND Found in superficial layers skin of

INCLUSIONS are nonliving components of a cell like: secretory granules, pigment, lipid, glycogen

Nucleus – contains genetic information

Cell Cycle _ _ _ The life of a somatic cell is a cyclic process - cell cycle consists of two periods: interphase and mitosis. interphase contains G 1, S, G 2 stages

CELL CYCLE: Stages G 1 Gap 1 S G 2 M G 1 Go growth, DNA Synthesis function (for new cells) stem Gap 2 formation of m. spindle, energy Mitosis or for Gap 1 for a new differen cycle tiation

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

Prophase _ Chromosomes become more coiled and visible _ the nuclear membrane breaks down _ Microtubules of centrioles form a spindle of division. Ch

Metaphase _ - chromosomes move to the center of the cell and form the equatorial plate Ch

Anaphase _ - the chromosomes separate and move to opposite poles of the cell Ch

Telophase _ - two daughter nuclei are formed. _ the chromosomes uncoiledand become indistinct.

EMBRYOGENESIS IS FORMATION OF THE HUMAN ORGANISM

Week 1 _ 1. Fertilization – is the fusion of the sperm and ovum = Zygote formation _ 2. Cleavage – is the division of the zygote in the uterine tube = Blastula formation

Week 1 Cleavage 2 cells stage 3 -5 cells stage Morula Blastula . . uterine tube zygote Fertilization uterus Implantation Day 6 - 8

At the end of cleavage outer cells (trophoblast) involve nutritive fluid, which forms cavity, moving inner cells (embryoblast). Blastula is formed. Inner Cell Mass (embryoblast) Trophoblast

Week 2. 3. Early Gastrulation (division and movement of cells). At the beginning of gastrulation (6, 7 day) germ sinks into the uterine wall – implantation. Gastrulation leads to formation of three germ layers – ectoderm, endoderm and mesoderm and extraembryonic organs: amnion, yolk sac chorion

Week 2 Ectoderm chorion amnion Endoderm yolk sac Extraembryonic Mesoderm of Amnion and Yolk Sac

Gastrulation is finished with the formation of axial organs – neural tube, notochord, somites (mesoderm), locating between ectoderm and endoderm. From them develop tissues and organs! Neural tube Somate amnion ectoderm endoderm yolk sac Notochord

4. Body flexion (amnion increases and forms body)

Body flexion formation (Gut formation. Gut is the upper part of yolk sac) longitudinally transversely gut head right left

Differentiation of germ layers and axial organs _ What develops from them?

Surface Ectoderm differentiates to skin, oral, rectal epithelium, corneal epithelium, tooth enamel amnion stomatodeum ectoderm

Endoderm differentiates to epithelium of stomach, intestine, liver, pancreas, respiratory, endocrine system -- 3 -4 weeks - gut endoderm gut

Extra mesoderm- formation of the first blood vessels in the wall of yolk sac and allantois blood vessels

Body Mesoderm urogenital system including kedneys, gonads, ducts, and accessory glands 3. Intermediate Mesoderm. Nephrotome dermatome - dermis of skin 1. Somitemyotome - muscles, sclerotome skeleton, except skull, 2. Lateral Mesoderm serous membranes of pleura, pericardium and peritoneum 4. Mesenchyme (loose part) – connective tissue of viscera and limbs, blood and lymph cells, vessels, smooth muscle

Late embryonic stages _ _ Histogenesis Organogenesis