Kharkov National Medical University

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Kharkov National Medical University

• Department of
• Histology, cytology and embryology

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HISTOLOGY

• studies microscopic structure and function of
  the human organism

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The Cell
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The Cell
is the structural and functional unit of the
organism
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Structure of a typical cell

1. Cell membrane
2. Nucleus
3. Cytoplasm

non-membranous organelles
cytosol
membranous organelles
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Biological membrane
Biological Membrane is a structural unit of a
cell
in the cell membrane, nucleus and
some organelles
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Cell membrane (plasmalemma). Outer is glycocalyx
glycocalyx
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Non-membranous Organelles

• 1. Cytoskeleton
• is the system of microtubules

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2. Cell center
2 centrioles consist of 9 triplets of
microtubules. Formation of mitotic spindle
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3. Ribosomes
two subunits - synthesize proteins Fixed on
RER, or free ribosomes
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Membranous Organelles
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1. Mitochondrion (two membranes) - synthesis
of energy - ATP
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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
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Packaging of proteins, formation of
lysosomes, secretion,
3. Golgi Apparatus
formation of compound molecules glycoproteins,
lipoproteins
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4. Lysosome is digestive apparatus, contains
enzymes(autolysis)
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Intercellular Junctions
1) Gap Junction

• has channel proteins

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2) Tight Junctions

• Interlocking proteins

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3) Desmosomes

• STRONG BOND
• Found in superficial layers
  of skin

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INCLUSIONS

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

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Nucleus contains genetic information
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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

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CELL CYCLE Stages
G1
S
M
G2
G1
Go
Gap 1 growth, function
DNA Synthesis (for new cells)
stem or for differentiation
Gap 2 formation of m.spindle, energy
Mitosis
Gap 1 for a new cycle
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Mitosis

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

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Prophase

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

Ch
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Metaphase

• - chromosomes move to the center of the cell and
  form the equatorial plate

Ch
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Anaphase
Ch

• - the chromosomes separate and move to opposite
  poles of the cell

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Telophase

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

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EMBRYOGENESIS

• IS FORMATION OF THE HUMAN ORGANISM

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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

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Week 1
3-5 cells stage
Cleavage 2 cells stage
Morula
Blastula
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uterus
.
uterine tube
Implantation Day 6 - 8
zygote Fertilization
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At the end of cleavage outer cells (trophoblast)
involve nutritive fluid, which forms cavity,
moving inner cells (embryoblast). Blastula is
formed.
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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
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Week 2
chorion

Extraembryonic Mesoderm of Amnion and Yolk Sac
Ectoderm
amnion
Endoderm
yolk sac
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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
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4. Body flexion (amnion increases and forms body)
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Body flexion formation(Gut formation. Gut is the
upper part of yolk sac) longitudinally
transversely
gut
head
right
left
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Differentiation of germ layers and axial organs

• What develops from them?

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Surface Ectoderm differentiates to skin, oral,
rectal epithelium, corneal epithelium, tooth
enamel
amnion ectoderm
stomatodeum
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Endoderm differentiates to epithelium of
stomach, intestine, liver, pancreas, respiratory,
endocrine system -- 3-4 weeks - gut
endoderm
gut
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Extra mesoderm- formation of the first blood
vessels in the wall of yolk sac and allantois
blood vessels
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Body Mesoderm
dermatome - dermis of skin myotome -
muscles, sclerotome - skeleton, except skull,
1. Somite
urogenital system including kedneys,
gonads, ducts, and accessory glands
3. Intermediate Mesoderm. Nephrotome
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
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Late embryonic stages

• Histogenesis
• Organogenesis

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The End