Download Ch 2: The Cell

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
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
glycocalyx
Non-membranous Organelles

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
of skin
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
G1
Gap 1
growth,
function
S
G2
M
G1
Go
DNA
Synthesis
(for new
cells)
stem
Gap 2
formation
of
m.spindle,
energy
Mitosis
or
Gap 1 for a for
new cycle differen
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