Tiêu đề Histology.pdf ✅

PURE BASIC | HISTOLOGY 1 w w w . p u r e b a s i c . c o m . b d | D r . S a r w e r B i p l o b Page 1 Pure Basic Histology 2020 For FCPS Part-1, MS & DDS Admission Preparation Dr. Sarwer Biplob BDS. FCPS (ii). MS (Course) Oral & Maxillofacial Surgery Medical Officer Faculty of Dentistry, BSMMU Founder, Pure Basic www.purebasic.com.bd 0163 888 5050
PURE BASIC | HISTOLOGY 2 w w w . p u r e b a s i c . c o m . b d | D r . S a r w e r B i p l o b Page 2 Cell Cell is the structural & functional unit of all living organism. Size,shape & number of cells:  Size varies from about 5 μm to 50 μm.  Shape may be flattened,cuboidal,columnar,fusiform,stellate,pyramidal,flask-shaped etc.  The human body comprises more than 200 different types of cells. Types: According to the structure of the nucleas there are two fundamental types of cells- 1. Prokaryotic 2. Eukaryotic Characteristic Prokaryotic Eukaryotic Size 0.2-2.0 μm in diameter 10-100 μm in diameter Nucleus Nucleoid/Nucleoli True nucleus Membrane enclosed organelles Absent Present Flagella Consist of two protein building blocks Complex. Consists of multiple microtubules Cell wall Usually present, chemically complex. When present chemically simple Plasma membrane No carbohydrates & generally lacks sterols Sterols & carbohydrates that serve as receptors Cytoplasm No cytoskeleton or cytoplasmic streaming Cytoskeleton. Cytoplasmic streaming Ribosomes 70s 80s Chromosome Single circular chromosomes, no histones Multiple linear chromosomes with histones Cell division Binary fission Mitosis Sexual recombination Transfer DNA fragments only,no meiosis Meiosis
PURE BASIC | HISTOLOGY 3 w w w . p u r e b a s i c . c o m . b d | D r . S a r w e r B i p l o b Page 3 Cell membrane: The thin,tough,elastic limiting membrane that separates the cytoplasm from the external environment, is called cell membrane or plasma membrane or plasmalemma. Thickness: 7.5 to 10 nm Composition:  protein -55%  lipids-42% phospholipids- 25% Cholesterol- 13% other lipids- 4%  Oligosachharides- 3% Structure of cell membrane: For the cell membrane, several models have been proposed. These are- 1. Unit membrane: Is composed of a trilaminar structure of two dense lines of lipid which is separated by a lucent intermediate layer. This three layered structure is known as unit membrane. 2.Fluid mosaic model:  Singer & Nicholson, in the early 1970s, proposed this model of membrane structure.
PURE BASIC | HISTOLOGY 4 w w w . p u r e b a s i c . c o m . b d | D r . S a r w e r B i p l o b Page 4  It proposes that the mosaic like globular membrane proteins are embedded or floating at variable depth in the fluid like lipid bilayer, like floating of the iceberg in a sea.  The membrane consists of a phospholipid double layer with proteins inserted in it (integral proteins) or bound to the cytoplasmic surface (peripheral proteins).  Carbohydrates in the form of oligosaccharides & polysaccharides are attached either to proteins (glycoprotein) or to lopids (glycolipids), projecting outwards from the surface of the membrane. 3. Protein - lipid sandwich: This model suggests that a protein coat is situated on both sides of the lipid bilayer to form a protein - lipid sandwich. Functions:  The plasma membrane gives boundary of the cell.  It maintains the shape of the cell.  It separates the protoplasmic contents of a cell from those of the neighbouring cells.  Acts as a selective barrier that regulates the passage of certain materials into & out of the cell  Facilitates the transport of specific molecules.  Regulates cell-cell interaction.  Acts as an interface between the cytoplasm & the external.  forms a sensory surface, specially in nerve & muscle cells.  Serves as a site of receptors  Performs a number of specific recognition & regulatory functions via receptors,antigens etc.  Maintains the structural integrity of the cell by membrane proteins.  Glycocalyx has a role in cell recognition & attachment to other cells & to extracellular molecules. Functions /Significance of membrane proteins: A. Integral Protein:  Acts as adhesion molecules that anchors cells to their neighbours or to basal lamina.  Acts as pumps: Transport ions across the membrane.  Acts as carriers: Transport substances by facilitated diffusion.  Acts as ion channels: When activated, permit the passage of ions into or out of the cells  Acts as receptors: Bind with neurotransmitters & hormones.  Acts as enzymes: Catalyzes reactions at the surface of the membrane.