Cell histology Flashcards
he smallest entity capable of independent existence. It is the basic morphologic and functional unit of all living things
Cell
Numerous species of unicellular organisms
germs- disease causing bacteria, parasites ex: entamoeba histolytica= amoebiasis)
how do humans start
single cell (fertilized ovum or zygote).
union of spermatozoon and ovum (male and female gametes respectively)
fertilization
Combination of tissues that form a more complex functional unit
Organ`
Combination of cells with the same general function
Tissue
Group of organs that have interrelated functions
Organ System
human cells (eukaryotic cells) share a common basic structure.
mass of cytoplasm
- cell membrane
- nucleus encased by nuclear envelope
- delimits cell from outside
- protective cover
- determines what can enter and exit
- binding sites and receptor for enzymes
- cell recognition
highly impermeable structure that does not allow molecules aside from water, gases and some molecules to pass freely
Cell Membrane (plasmalemma)
Cell Membrane
- 2 layers of phospholipids
head and 2 tails
head of cell membrane
globular and polar (hydrophobic)
glycerol (outer region)
Tail= Saturated and unsaturated fatty acid
Nonpolar (Hydrophobic) One tail contains saturated FA The other tail contains unsaturated FA Has a slight kink but otherwise straight Linkage between the head and the tail involves covalent bonds
- half mass of the cell membrane
- transport substances
- signal transduction
- cell recognition
protein
2 types of protein
transmembrane protein
peripheral membrane
Loosely attached to the inner or outer surfaces of the membrane
peripheral membrane
Project out of the inner and outer surfaces of the membrane
Transmembrane proteins
whats in the cell membrane
cell membrane mainly contains proteins, phospholipids but also cholesterol and polysaccharides such as glycolipids and glycoprotein
- almost as many as phosolipid
- in irregular spaces
- makes cell m. less permeable to water soluble
- harmful if excess in blood = plaques
CHOLESTEROL
- in the forms of glycolipids & glycoproteins
- project out of the cell to form a coating called Glycocalyx
- nvolved in cell-to-cell recognition, cell-to-cell adhesion
- immune response
polysaccharides
also known as the unit membrane
of matrix (cytosol) where formed elements are embedded (organelles, inclusions & fibrillar structures)
CYTOPLASM
viscid, translucent and colloidal substance which is the site of important biochemical processes
- suitable environment for organelles to work
>70% water: inorganic
Matrix
- alwayys in cytoplasm
- has specific functions
all cells have organelles - ## except rbc and lens fiber
Formed elements (organelles)
Typical organelles in a human cell :
Mitochondria Ribosomes RER & SER Golgi Apparatus Lysosome Peroxisome Centrosome (contains centrioles)
he cell “powerhouse”
They are able to produce energy because the
- hotdog-shape or rod like spherical
- Mitochondria can only be produced from existing mitochondria.
Mitochondria
on what does rbc and muscle cells rely
who dont have mitochondria
Glycolysis
Distributes proteins throughout the cell
Smooth ER
Site of
synthesis of protein for cell maintenance
and metabolic processes
- synthesis of protein component
- packages proteins for rer
Golgi Apparatus
Source of the microtubules for cell use
-Microtubule Organizing Center (MTOC
Centrosome (MTOC)
- recycles protein
- prtects function from foreign bodies
- phagocytosis
- heterophagy
- autophagy
Lysosomes
Prevent degradation of the neuron through
its detoxification function
-Catalase = H2O2 O2 +H2O
Peroxisomes
- form part of the proteins of structures that are needed to be renewed (microtubules/ microfilaments)
- ## form cytplasmic matrix
ribosomes
Most extensive membrane-bound structure in the cytoplasm
-
RER & SER
There are ribosomes and polyribosomes attached to its membranes
Rough ER-
responsible for bone ressorption which releases their hydrolytic enzymes extracellularly
Osteoclast
Digestion of substances foreign to the cell
Heterophagy
Digestion of unneeded organelles or any structures within the cell
Autophagy
most important phagocytes are
neutrophils and macrophages
LYSOSOMAL ENZYMES
Digest all cellular organic matter
Active at pH 5
Inactive at pH7.2 (cytosol)
formed by tubular structures known as microtubules
- ## Source of mitotic spindle fibers (mitosis), Cilia of ciliated cells and tail of sperm cells (flagella)
CENTRIOLE
Inclusions
Fat droplets glycogen zymogen granules pigment granules crystals dust particles
Temporary inert cellular structures which may or may not be membrane bound
Some are harmful and some are useful
INCLUSIONS
- specialized in storing lipids.
- ## occupy more than 90% of the cell
Fat Droplets (Lipid droplets)
- The storage form of carbohydrates
- ## present in many cells, particularly abundant in liver and muscle cells.
Glycogen (Glycogen Granules
- membrane bound proteins from golgi complex released by the cell to the extracellular space via exocytosis
Zymogen Granules
Pigment Granules
- melanin
- hemosiderin
- ## lipochrome
- Brown to black coloration of the skin
is present in nerve cells of substantia nigra & locus coeruleus in the
Melanin
- Brown pigment which is the product from the lysosomal digestion of hemoglobin
- Residual bodies= membrane bound
Hemosiderin
Yellowish-brown pigments in long-lived cells such as the muscle cells in the myocardium, Sertoli cells in the testes, neurons and
Lipochrome
Rod shaped but can also occur in other shapes
No known function
Probably degenerative cells as they are presently
present in interstitial cells of Leydig in testes & Sertoli cells of testes)
Crystals
Brown to black membrane-bound structures
Numerous in a smoker’s lungs and in people who live in a dense dusty environment
Dust Particles
A complex network of fibrillar elements that forms the structural framework’ or skeleton of the cell.
CYTOSKELETON
3 types of fibrillar elements classified to diameter
- MICROFILAMENTS
- INTERMEDIATE FILAMENTS
- MICROTUBULES
- present in all cells
- a lot in peripheral area to provide internal cellular support
- actin makes up 10-15% of total cellular protein
MICROFILAMENTS
- Not exclusively seen in cytoplasm
Some are present in the nucleus - ## has 5 major types
INTERMEDIATE FILAMENTS
Major types (Cytoplasm) INTERMEDIATE FILAMENTS
Keratin Desmin (skeleton) Vimentin Neurofilament Glial filament (glial fibrillary acidic protein: GFA)
a type of intermediate filament
- in epithelial cells
- Protects cells from mechanical and oher stresses
Keratin
a type of intermediate filament
- found in muscle
- man in smooth muscles
- maintain cell archi and structure
desmin (skeleton)
a type of intermediate filament - in mesenchyme derived cells - scattered all over cytoplasm - help maintain cell shape -
vimetin
a type of intermediate filament
- in nerve cells
- cell body and process of neurons
- parelle to axis
neurofilament
a type of intermediate filament
- in neuroglial cells
- facilitates internal support
glial filament
the thickest among the three
- Hollow pipes assembled/ disassembled in the centrosome
- 13 tubulin molecules.
- In the cytoplasm = support of the cell
Embedded in organelles = movement
Comprises the centrioles, mitotic spindles, cilia of ciliated cells and flagellum of sperm cells
MICROTUBULES
- largest structure
- in all cells except rbs
- round
- nucleated,
- nucleus data bank
- Site for RNA production needed for the protein synthesis which cytoplasmically occur
rRNA (ribosomal)
mRNA (messenger)
tRNA (transfer)
NUCLEUS
nuclear envelope (nuclear membrane)
- 2 unit membranes (outer and inner nuclear
- fluid filled
- nuclear pores are round opening 100 pores
NUCLEAR ENVELOPE
A fibril protein layer is associated with the inner surface of the inner nuclear membrane
-Serves as mechanical support of nucleus
Stabilizes nuclear pores
Fibrous Lamina
- made of nucleoplasm/ nuclear sap
- Chromosomes are embedded here
- chromosomes are referred to as chromatin/ chromatin materials (INTERPHASE)
Nucleolus is usu
NUCLEAR MATRIX
- Nucleus of all human cells contain 46 chromosomes (
- 23/46 is inherited from the moth, half from father
- Numbered according to length 1-22
-Female sex chromosomes are homologous, male are not
CHROMATIN
Chromatin forms granules or clumps
- takes up stains
- darker
- not all produce RNA
Heterochromatin
Areas that do not take up stains Made up of portions of chromosomes which are - no stains - lighter color - mrna and trna made here
Euchromatin
All DNA molecules in the human cell
HUMAN GENOME
-DNA in chromosomes
Larger than mitochondrial genome
Largely referred to human genome
Database of coding sequences for all protein and nucleic acid
Chromosomal genome
DNA in mitochondria
Contains coding sequences for proteins and enzymes it needs and for replication
- 5% encode for genes.
Mitochondrial genome
- Only seen at interphase
- Only 1 nucleolus in nucleus
- ## Absent in cells that do not synthesize proteins or may synthesize small proteins
NUCLEOLUS
Site of ribosomal subunit synthesis
- Nucleolar organizing region
- Pars fibrosa
- Pars Granulosa
NOR – circular pale are surrounded by electron-dense filament
- Site of gathering of chromosomes which have NOR
- Refers to gene coding for rRNA
Nucleolar organizing region
Electron-dense area surrounding NOR
Consists of rRNA from NOR
Pars fibrosa
Granular area surrounding Pars fibrosa
The rRNA from pars fibrosa will get linked to proteins
Pars Granulosa
One of the most important activities of a cell is the production or synthesis of proteins.
- protein is essential to cells
- catalyze biochemical reactions and hormones and hormone-like substances
-
PROTEIN SYNTHESIS
PROTEIN = POLYPEPTIDE CHAIN CONTAINING AMINO ACIDS LINKED VIA PEPTIDE BONDS
where is the amino acid code sequence produced
nucleus
Amino acid into polypeptide chain happens in the
cytoplasm
Diffusion, ion channels, carrier transport and active pump transports =
- bigger molecules transported via bulk transport
CELL MEMBRANE TRANSPORT
Liquid substances are passing through the membrane
MICROPINOCYTOSIS
Solid substances are passing through the membrane
PHAGOCYTOSIS
chemical
Engulf microscopic or small amount of liquid
MICROPINOCYTOSIS
Engulf large amount of liquid
MACROPINOCYTOSIS
Entry of molecule into the cell
ENDOCYTOSIS
Exit of molecule out of the cell
Most materials transported out of the cell ar
EXOCYTOSIS
First accumulates in cell apex then later released simultaneously in response to stimulus
REGULATED SECRETION
The secretory granules are released immediately after they leave the golgi complex
CONSTITUTIVE SECRETION