Medical Histology PDF

MEDICAL HISTOLOGY INTRODUCTION OTHER PARTS OF EUKARYOTIC CELLS HISTOLOGY: is the study of all aspects of tissue 1. MITOCHONDRIA biology of the body.  Tissue arrangements to constitute organs  F...

MEDICAL HISTOLOGY INTRODUCTION OTHER PARTS OF EUKARYOTIC CELLS HISTOLOGY: is the study of all aspects of tissue 1. MITOCHONDRIA biology of the body.  Tissue arrangements to constitute organs  Functions of different cells and tissues  Interacting components: Cells and the ECM Structure:  sausage-shaped organelle THE CELL  with inner (contains folds to increase EUKARYOTIC CELL the surface area) and outer (surrounds the entire organelle) membrane.  contains membrane-bound organelles  possess intramembranous space such as clearly defined nucleus. (space between the outer and inner  basis for every multicellular organism, membrane) including animals, plants, and human. Cristae: folds inside the mitochondria. Functions: A. ATP PRODUCTION  via oxidative phosphorylation (the addition of phosphate; the final stage of cellular respiration involving the ETC and chemiosmosis). MAJOR PARTS OF EUKARYOTIC CELLS ATP synthase: enzymes needed to produce ATP 1. NUCLEUS: separated from the (located within cristae) protoplasm by a nuclear membrane which contains nearly all cell’s DNA. *ATP is NOT energy 2. CYTOPLASM: separated from the - rather a carrier or storage for potential extracellular fluid (ECF) by a cell. energy within its chemical bonds. - the last phosphate group contains high- *Protoplasm: refers to the entire living content energy chemical bond. within a cell, including the cytoplasm and nucleus. (cytoplasm + nucleus) *Cytoplasm: refers to everything inside the cell membrane excluding the nucleus. (cytosol +organelles) *Cytosol: the fluid component in which organelles are suspended. B. REGULATION OF APOPTOSIS release apoptogenic proteins that signals cascade of events for cell death. Proteins and factors involved: a) Cytochrome C b) Smac/DIABLO c) Apoptosis Inducing Factor (AIF) d) Omi  2. NUCLEUS 4. GOLGI APPARATUS  Control center of the cell which  Packaging center contains DNA. of the cells Cisternae Structure DNA→ CHROMATIN→ CHROMOSOME - folds of Golgi Apparatus DNA: carries the genetic instructions used in the growth and development. 2 sides of GA: CHROMATIN: complex of DNA and proteins A. Cis face: where the vesicles enter from (mainly histones) that make up the ER chromosomes. B. Trans face: where the vesicles exit Forms:  EUCHROMATIN: loosely packed 5. LYSOSOME chromatin; genes are accessible for transcription and more like to be expressed.  HETEROCHROMATIN: densely packed chromatin; genes are generally not expressed. CHROMOSOMES: condensed and highly organized form of chromatin. Structure: NUCLEOSOMES: basic unit of chromatin which  no definite shape (irregular) contains a segment of DNA.  plasma membrane of lysosome is GENOME: complete set of genetic material in also a phospholipid bilayer (came an organism (genes + non-coding regions in from Golgi Apparatus) the DNA sequence) GENES: specific sequence of DNA that encodes Functions: instructions for building proteins. A. DIGESTIVE SYSTEM OF THE CELL  contains hydrolytic enzymes 3. ENDOPLASMIC RETICULUM collectively termed as acid  Factories of the cell hydrolases.  Inner membrane attached to the nuclear membrane. Two regions: A. ROUGH ENDOPLASMIC RETICULUM (granular form)  Contains ribosomes → functions for protein synthesis Two subunits in eukaryotes: 60s and 40s subunits B. ACIDIC ENVIRONMENT Ribosomes: made of RNA and proteins pH of 5: optimal pH for acid hydrolases; (ribonucleoproteins structure) dangerous and acidic - rRNA (ribosomal RNA) pH of cytosol is around 7.4: *Should there be an escape of lysosomal B. SMOOTH ENDOPLASMIC RETICULUM contents, the pH will be inactivated due to the (agranular form) higher pH of cytosol (FOR SAFETY MEASURES)  No ribosomes → functions for lipid LYSOSOMAL STORAGE DISEASES synthesis 1. TAY-SACHS DISEASE  Absence of hexosaminidase A  Accumulation of gangliosides  2. MUCOPOLYSACCHARIDOSIS 1. PROTEINS (55%)  Absence of beta-glucuronidase Types of membrane proteins:  Accumulation of glycosaminoglycans a) Integral proteins embedded within/ traverses the membrane 6. PEROXISOME  provides structural channels or  aka microbodies pores for substances to pass  membrane of peroxisome is also through phospholipid bilayer (came from b) Peripheral proteins located on one smooth ER) side (either inner or outer)  specialized in lipid biosynthesis  acts as enzymes or controllers of  contains crystalline core (urate the transport of substances oxidase) Functions of membrane proteins: Functions: a) Adhesion molecules – adhesion to 1. BUILDER basal lamina, other cells,  Enzyme oxidase communication with other cells a. Specialized in lipid biosynthesis b) Pumps– Facilitate or regulate the - plasmalogens (lipid in myelin concentration of ions sheath): speeds up transmission c) Ion channels– Movement of molecules - lipids in bile acids (selective permeability) b. Synthesis of hydrogen peroxide d) Receptors– Serves as the binding sites c. Synthesis of superoxides e) Ligands – substances that binds with receptors (drugs and other chemical 2. DESTROYER substances)  Enzyme catalase f) Neurotransmitters – Signaling  Catalase uses hydrogen peroxide molecules (acetylcholine, to detoxify substances such as norepinephrine, epinephrine) phenols and alcohols (acetaldehyde). 2. LIPIDS (42%)  Breakdown of lipids: works with lysosome 7. PLASMA MEMBRANE  Aka cell membrane or plasmalemma  Envelopes every eukaryotic cells Types of membrane lipids: a) Phospholipids– Phospholipid bilayer Composition of cell membrane:  Phosphatidylcholine– functions for transmembrane A. Proteins (55%) signaling activation of B. Phospholipids (25%) enzymes for metabolic C. Cholesterol (13%) reactions; acts as surfactant D. Other lipids (4%) E. Carbohydrates (1-3%)   Phosphatidylethanolamine– PLASMA MEMBRANE functions for membrane fusion and for cell division While cell membrane is defined to be just the outer part of the cell, some proteins extends b) Glycosphingolipids– transmembrane inside the cell. signaling c) Sphingomyelin– transmembrane TRANSMEMBRANE PROTEINS AND MEMBRANE signaling TRANSPORT d) Cholesterol- maintains cell membrane 1. PASSIVE TRANSPORT fluidity to allow movement of proteins 2. ACTIVE TRANSPORT 3. INTERACTING COMPONENTS: CELLS AND ECM PASSIVE TRANSPORT  Groups of proteins and other  Movement of molecules or ions across molecules outside the cell or tissues. a cell membrane without the input of  these molecules may extend inwards energy. depending on the function of cells and tissues. Plasma membrane: site where materials are exchanged between cells and environment. 1. DIFFUSION: allows transport of small molecules, nonpolar molecules and lipophilic (fat-soluble). The cell Water passes the membrane at a very slow rate 2. CHANNELS: proteins forming transmembrane pores; ions and molecules pass selectively. Closing and opening occurs for some ions: Ca2+, Na+, K+.  Aquaporins: channels used by water 2. PINOCYTOSIS: aka cell drinking molecules. 3. CARRIER: transmembrane proteins that bind small molecules and transport them via conformational change.  Other large water- soluble molecules ACTIVE TRANSPORT 1. TRANSPORT BY VESICLES  Enclosing the molecule (smaller invaginations) Molecules enclosed by the plasma membrane  Fusion of membrane → after binding specific receptors → Fusion  Pinching off of membrane → pinching off → Vesicles  Formation of vacuoles (vacuoles) - Pinocytotic vesicles TRANSCYTOSIS 3. RECEPTOR-MEDIATED ENDOCYTOSIS ENDOCYTOSIS: process in which a cell takes in materials from the extracellular environment by engulfing them with its cell membrane. 3 MAJOR TYPES OF ENDOCYTOSIS 1. PHAGOCYTOSIS: aka cell eating  Integral proteins as receptors; high affinity with ligands  Ligands bind to receptor proteins  Ligands aggregate in one membrane region  Invagination occurs vesicle - Endosomes  Formation of pseudopodia - membrane-bound  Enclosing the molecule compartments that play a critical role  Fusion of membrane in determining the fates of internalized  Pinching off molecules, directing toward recycling  Formation of vacuoles pathways or degradation in lysosomes. - Phagosomes (specialized intracellular vesicles formed) LYSOSOME Adaptor proteins: recruit clarithin to the plasma membrane and select specific cargo molecules for endocytosis by binding to cargo receptors. Clarithin: protein that bends the membrane, creating a clarithin-coated pits that eventually bud off to form vesicles. Dynamin: responsible for the final scission of the vesicle from the plasma membrane.