ANAT2008 Flashcards
Cytology
Study of the structure of cells
Histology
Study of Tissues
5 Types of Tissues
Can classify the basic tissues types by identifying the basic arrangement of cells.
- Epithelial
- Connective
- Muscular
- Nervous
- Adipose
Epithelial Tissue
Separates the body from the environment e.g skin
Cells are tightly packed together
Often responsible for major work
Connective Tissue
Holds other tissues types together
Cells packed loosely
Nervous Tissue
Consists of cells called neurons (specialised to conduct electrical impulses)
Cells packed tightly
Muscle Tissue
Contain cells specialised for contraction
Cells not normally closely packed
Different types: smooth, skeletal, heart
Adipose Tissue (fat)
Consists of cells which contain lipids
Cells separated by narrow spaces but not as tightly packed as epithelial
Type of connective tissue
Micrometer
um
10^-6 M
Nanometer
nm
10^-9 M
Cell Theory
- Living things only consist of cells and the products of cells.
- Cells consist of one of more nuclei surrounded by a nuclear membrane which is surrounded by a cytoplasm containing organelles which is, in turn, surrounded by a plasma membrane.
- All cells arise from pre-existing cells by cell division (life arose once on this planet and then evolved).
Two Principle Types of Cells
- Prokaryotic: genetic material not contained within a specific unit.
- Eukaryotic: genetic material contained within a particular site (nucleus).
The Plasma Membrane
Surrounds cell
Semi-permeable (selects what enters and exits the cell)
Trilaminar appearance: 3 layers (dark, light, dark)
Made up of three molecules: lipids, proteins and carbohydrates.
Plasma Membrane - Fluid Mosaic Model
Phospholipid bi-layer: hydrophobic heads and hydrophobic tails.
Integral Proteins: Pass into membrane.
Peripheral Proteins: on edge of bi-layer
Carbohydrates: contently bonded to lipids and proteins, found only on outer surface of membrane, form glycocalyx (seen with electron microscope).
NOTE: the plasma membrane is the only membrane with the glycocalyx
Plasma Membrane - Freeze Fracture Technique
Rapidly freeze a cell and then hit it with a knife. Fractures the membrane and allows it to be examined using a microscope.
Provides a visual conformation that the fluid mosaic model accurately depicts the arrangement of lipids, proteins and carbohydrates.
Plasma Membrane - Functions
Regulates the movement of molecules in and out of a cell.
Ion transport: passive and active
Receptor sites
Exocytosis and Endocytosis
Cohesion: the plasma membranes of cells stick together to form tissues.
Communication
Cytoskeleton
Located within the cytosol
Seen under the microscope when stained
Microtubles, microfilaments and intermediate filaments
Cytoskeleton - microtubles
Made of a protein called tublin
24nm in diameter
Vary in length -> tubular molecules added or subtracted to each end
Transport
Cytoskeleton - microfilaments
Actin and myosin
Located under cell membrane - stabilize
Cytoskeleton - intermediate filaments
Different in different eukaryotic cells - made up of different proteins -> can be used as a diagnostic tool.
Cytoskeleton - Function
Maintain cell shape
Intracellular transport
Movement of cells e.g during phagocytosis
Cellular reception e.g hearing
Centriole
Pair near nucleus
Tubular structure: 9 groups of 3 microtubles form the wall of a centriole
Centriole - Function
Master organiser of cell shape Cell division (produces spindle fibres) Creates basal body (critical structure in formation of cilia)
Ribosomes
Equal parts protein and RNA Free in cytoplasm or attached to ER Individual or in groups (polysomes) Ribosomes in polysomes are active -> spiral structure Synthesise protein
Endomembrane System
Nuclear envelope, golgi body, ER
Endoplasmic Reticulum
Two shapes -> tubular + cisternae (sheets)
Rough ER and Smooth ER
Rough ER
Cisternae structure
Ribosomes attached
Proteins synthesised
Smooth ER
Tubular shape No ribosomes Synthesis of steroids ( cells which secrete steroids e.g ovaries have a lot of smooth ER) Contain enzymes which detoxify drugs Transport of ions Breaking down of carbohydrates
Golgi Body
Packages proteins for secretion
Proteins produced by ribosomes on the RER packaged into transport vesicles -> enter Golgi -> golgi packages proteins into large secretory vesicles -> secretory vesicles fuse together to form secretory granules and then exit the cell by exocytosis
ALSO modifies proteins (post translation modification -> required for some proteins to be active).
Trans Golgi Network
Collection of membranes associated with RER and golgi -> produce lysosomes
Lysosomes
Darkly stained vesicles
Formed in trans golgi network -> part of membrane buds off -> enzymes added
Intracellular digestion
Lysosomes - heterophagy
Cell digests material different from itself
1. phagocytosis = large insoluble materials ingested -> fuse to form a phagosome
2. endocytosis = small soluble materials ingested -> fuse to form an endosome
Phagosomes + endosomes fuse with lysosomes and are broken down.
Lysosomes - autophagy
Cells digest their own damaged or unwanted components
Vesicles form around unwanted part -> autophagosome -> fuse with lysosome
Deroxisomes
Vesicles related to lysosomes
Contain catalyse ->able to break down hydrogen peroxide (toxic biproduct of cellular metabolism)
Mitochondria
Outer membrane: Smooth -> defines shape of organelle
Inner membrane: folded (cristae) -> more cristae = more energy produced.
Matrix: gel substance in mitochondria
Contain some of their own DNA -> synthesis some of the proteins involved in ATP production.
Nucleus - nuclear envelope
Double membrane
Regulates what enters + exits
Pores -> made up of a ring of proteins
Nucleus - nucleoplasm
No membrane -> diffusion of molecules
40% protein and therefore most likely highly organised
Nucleus - nucleolus
Dense rounded structure
The bigger the nucleolus the more active the cell
Contain rRNA, ribosomal protein + DNA -> synthesis and pre-assembly of ribosomes
Nucleus - Chromatin
DNA + protein
Heterochromatin: chromosome state -> more densely packed -> darkly stained -> inactive DNA
Euchromatin: nucleosome or solenoid state -> loosely packed -> lighter stain -> active DNA
THE MORE ACTIVE A CELL THE LIGHT ITS NUCLEUS
Epithelial Tissue
Separates constant internal environment from hostile external environment e.g digestive tract, lungs
Endothelium: lines blood vessels
Mesothelium: lines all hollow organs except the heart
Epithelial Tissue - Structural and Functional Characteristics
Cellularity Polarity Specilized contacts Lateral communication Basal Lamina Cell replacement
Epithelial Tissue - Cellularity
Tissue only consists of epithelial cells
Tightly packed together in sheets
Stains darkly
Epithelial Tissue - Polarity
Cells are polarised (different at different ends)
Apical = faces outside
Basal = faces inside
Lateral = sides
Differences seen in different specializations of the plasma membrane.
Epithelial Tissue - Specilized Contacts
Junctions
Epithelial Tissue - Lateral Communication
Pass information sideways -> made possible by the GAP junction in the plasma membrane
Epithelial Tissue - Basal Laminar
Fine layer of proteins and filaments -> epithelial cells connected to it
Supports cells, filters, defines the space where epithelial cells are supposed to exist.
Epithelial Tissue - Cell Replacement
Very high rate -> consequence of being exposed to toxic environment
More replication = more likely to mutate -> cell replicate away from external environment and move upwards.
Epithelial Cells: Specilizations of the apical plasma membrane
- Special Proteins: glycoproteins (receptors), alkaline phosphate (removes phosphate group), integral proteins, transport molecules.
- Microvilli: projection of the plasma membrane -> increase SA. Actin filaments run through the microvilli and join to a horizontal group of actin filaments (terminal web)
- Stereocilia: Long microvili -> increase SA + sensory receptors.
- Cilia + Flagella: motile structures. Cilia -> move fluid over a cell’s surface -> special arrangement of microtubles (axoneme) 9 pairs of microtubles and 2 in the center.
Epithelial Cells: Specilizations of the Lateral plasma membrane
- Proteins: associated with transport in + out of the cell
2. Specialized junctions: Tight junction, adherence junction, desmosomes, GAP junction.
Lateral Plasma Membrane Epithelial: Tight Junction
Proteins in adjacent cells make head-to-head contact -> ‘zipper’ cells together -> reduces the movement of molecules from outside down in between cells.
Tight = no movement of substances
Loose = movement of some substances between cells.
Lateral Plasma Membrane Epithelial: Adherence Junctions
Ring of cadherens proteins all around the top of the cell -> strengthens + reinforces the apex of the cell.
Lateral Plasma Membrane Epithelial: Desosomes
Specific spot where intermediate filaments run into cytoplasmic plate + transmember linkers link the plates of adjacent cells.
Lateral Plasma Membrane Epithelial: GAP Junction
Connexin proteins make head-to-head contact -> have a small pore in center -> allow passage of small molecules
Epithelial Cells: Specilizations of the Basal plasma membrane
- Hemi-desmosomes: anchor cell to underlying connective tissue
- Pedicles: protrusions of the plasma membrane into undelying connective tissue -> increase SA for adhesion.
- Membrane infolding: Fold = more plasma membrane = more ion pumps = more efficient. Mitochondria = needed to fuel active transport of ion pumps.
Epithelial: Simple Squamous
Found in areas of exchange: aveoli + kidney
Thin, leaky tight junctions + lost of vesicles
Epithelial: Simple Cuboidal
Kidney tubles, reproductive tract, thyroid
Absorption and/or secretion