CTL Flashcards
Describe homeostasis
Homeostasis is the stable internal environment in which the constituents of the body (i.e. cells, proteins, enzymes, etc.) function. This is maintained despite the ever-changing external world.
What is the Principle of Complementarity of Structure?
The principle states that anatomical structure is intrinsically linked with physiological function; structure and function are dependent off each other
Outline the organisation of the body
Molecules -> Cells -> Tissues -> Organs -> Systems -> Body
Outline Cell Theory
- Cells are the most basic functional units of life
- Cells are alive and dynamically changing
- Cell structure and function are intrinsically linked
- Cells have a ‘life cycle’ known as the cell cycle
What are the stages of the cell cycle?
Cell is predominantly in Interphase but will go into mitotic phases when replicating
Outline Interphase
- G1: the cell grows and is metabolically active
- S: DNA begins to replicate (synthesis stage)
- G2: Cell finishes growing; enzymes and other proteins are synthesised; DNA replication is completed
What is the first phase of Mitosis and what occurs?
Prophase: DNA (chromatin) condenses into chromosomes and the mitotic spindle begins to form (nucleus disappears)
What is the second phase of Mitosis and what occurs?
Metaphase: Chromosomes are lined on the metaphase plate of cell by microtubules (centromeres are in the exact centre)
What is the third phase of Mitosis and what occurs?
Anaphase: Spindle fibres shorten, causing chromosomes to separate at centromeres. The sister chromatids then move to opposite poles of the cell
What is the fourth phase of Mitosis and what occurs?
Telophase: Following chromatid movement, a nucleus reappears around the chromatids. The chromatids uncoil into chromatin
What is the final phase of Mitosis and what occurs?
Cytokinesis: The cell is cleaved into two identical daughter cells
What type of cell is Bacteria?
Prokaryote cell (no nucleus)
What type of cells do humans have?
Eukaryote cells (membrane-bound nucleus)
Compare and contrast prokaryote and eukaryotes (size; cell wall; nucleus; genetic material; membrane-bound organelles; plasma membrane; endoplasmic reticulum; ribosomes and reproduction)
- Size: prokaryotes significantly smaller than eukaryotes
- Cell wall: always present in prokaryotes, sometimes present in eukaryotes
- Nucleus: prokaryotes have no defined nucleus, eukaryotes do
- Genetic material: prokaryotes have one circular chromosome, eukaryotes have multiple
- Membrane-bound organelles: only present in eukaryotes
- Plasma membrane: present in both types
- Endoplasmic Reticulum: only present in eukaryotes
- Ribosomes: smaller in prokaryotes (70s), larger in eukaryotes (80s)
- Reproduction: prokaryotes are largely asexual, eukaryotes are asexual and sexual
How does a Gram-positive Bacteria differ from a Gram-negative Bacteria?
- Gram positive bacteria have a thick outer layer of peptidoglycan (PG)
- Gram negative bacteria have a PG layer sandwiched between two membranes
What colour are Gram Postive and Gram Negative Bacteria?
- Gram Positive: blue/purple
- Gram Negative: red/pink
What is a key feature of antibiotic drugs?
Selective toxicity, they only kill target organisms and not host cells
What are the four main target sites for antibiotics?
- Inhibition of cell wall synthesis
- Inhibition of protein synthesis
- Inhibition of nucleic acid synthesis
- Disruption of cell membrane function
What is a bactericidal drug and how does it differ from a bacteriostatic?
Bactericidals kill bacteria, whereas bacteriostatics only slow growth/replication
Outline the three main structural features found in most cells
- Cell membrane: forms a barrier and allows cells to be self-contained
- Nucleus: the control centre of the cell responsible for cell activity
- Cytoplasm: intracellular solution that houses all organelles and structures required for function
Where would you find integral and peripheral proteins? What are their functions?
On plasma membrane.
Integral proteins are a functional part of the cell membrane– drive cell activity. Peripheral proteins include receptors that stimulate intracellular activity
What are some functions of the cell membrane?
Transport; providing receptors for signal transduction; controlling cytoskeleton; enzymatic activity; intracellular joining and cell-cell recognition
How are cells joined? Briefly describe.
Cell junctions.
Tight Junctions: binding connection where extracellular fluid space is eliminated to prevent substances from passing in between cells
Desmosomes: anchored junction (bound by plaques and collagen)
Gap Junctions: a functional connection allowing the movement of molecules between cells
What are the two different transport mechanisms used by cells? How do they differ?
Passive and active transport. Passive transport relies on materials moving along concentration gradients; active transport utilises energy to move things against concentration gradients
What is the function of the mitochondria?
The mitochondria is the organelle responsible for energy production in a cell
What is the function of the Endoplasmic Reticulum (ER)
Rough ER has ribosomes which synthesis proteins; Smooth ER synthesises lipids and carbohydrates
What is the function of the Golgi Apparatus
The Golgi Apparatus modifies, packages and transports various proteins from the Rough ER. It receives proteins from its cis-face and transports via the trans-face
What does a lysosome do?
Lysosomes are responsible for breaking down and digesting various toxins or old/damaged parts of the cell
How does the cell move?
The cell moves thanks to the cytoskeleton (cell skeleton) and the centrosomes, which contain centrioles (microtubules)
Cilia and microvilli are examples of what?
They are cellular extensions, which are projections of the cell membrane
What are the four different cell types in the body?
Epithelia; connective; muscle and nervous
What are epithelial cells?
Cells that line the external and internal surfaces of the body. They also form boundaries and coverings of various body structures.
What are some key characteristics of epithelial cells?
They adhere to nearby cells (to form barriers); they have polarity (functional); proliferation (high turn-over rate due to high traffic areas); avascular (no direct blood supply because of frequent damage) and they are anchored to connective tissue
Epithelia can be classified as…
Layering and cell types
- Simple: a single layer of cells
- Stratified: multiple layers of cells
- Pseudostratified: simple, but appearance of stratified due to new cell proliferation (shark teeth)
- Squamous: very flat shape (decreased cytoplasm activity)
- Cuboidal: solid, square shape
- Columnar: solid, elongated shape
-Transitional epithelia: only found in bladder, can stretch
Define an exocrine gland
An exocrine gland is a specialised epithelia that secretes a product on to an epithelial surface via a duct system
How do exocrine/endocrine glands form?
Specialised epithelia invaginate, if access to the surface is retained– exocrine. If completely cut off– endocrine.
How do unicellular and multicellular exocrine glands differ?
Unicellular made solely of secretory unit (acinus); multicellular consists of secretory unit and duct
What is merocine secretion?
Exocytosis– expulsion of a vesicle’s contents into the extracellular environment
What is holocrine secretion?
Product accumulates inside cell. Eventually the cell bursts open, releasing the contents
What are the three main epithelial membranes?
Cutaneous; serous and mucosal
Define cutaneous membranes
Cutaneous protects the body from the direct external surface (skin). It is composed of the epidermis (protective layer) and the dermis (sensitive and glandular layer)
Define serous membranes
Moist membrane that contains serous fluid. The fluid acts as a biological lubricant that aids in friction-less movement. Found in the pleura (lungs); pericardium (heart) and peritoneum (abdominal organs)
Define mucosal membranes
Membranes covered by a layer of thick mucous. These are usually found in openings that are exposed to the outside world. The mucous traps foreign particles and protects the epithelia
What is the name of the two components that make up the basement membrane of epithelia?
Basal lamina and the reticular lamina
What is the function of the basement membrane?
The basement membrane connects the epithelia to the connective tissue. It also supports the overlying epithelia layer, allows epithelial cells to move along it during healing and cell migration, and prevents substances from passing through the epithelial layer into the CT layer
What is connective tissue?
Connective tissue is made up of cells in an extracellular matrix. CT functions to provide support for organs, provide protection (via immune response), insulation and transport (via blood vessels)
What does extracellular matrix consist of?
It consists of fibres and a ground substance. The composition of both of these varies depending on function of the CT
What are the three fibres found in ECM? What are their qualities?
- Collagen: strong fibre that is resistant to stretching and tension
- Reticular: type of collagen that forms a loose interwoven network
- Elastic/elastin: flexible and resistant to deformation
What is the embryonic origin of CT?
Mesenchyme
Connective tissue can be categorised under three macro-headings. What are they?
CT proper; Supporting CT and Fluid CT
What are the two main types of CT proper?
Loose and Dense CT
Give an example of Loose and Dense CT
Loose CT: areolar, adipose or reticular
Dense CT: regular, irregular or elastic
What are the two main types of supporting CT?
Cartilage and Bone
Given an example of cartilage and bone
Cartilage: hyaline, fibrocartilage or elastic
Bone: compact or spongy
What is the only type of fluid connective tissue?
Blood
Cells in CT can be “-blasts” or “-cytes”. Explain the difference and why this occurs
“-blasts” are immature “stem cells”; “-cytes” are mature cells. This occurs to allow the CT to constantly grow and adapt
What are the two main types of cells in CT proper? What are their main functions?
- Resident cells: maintain and repair the ECM; storage
- Wanderer cells: repair damaged ECM; immune response
Name two types of resident and wanderer cells respectively. What are their functions?
Resident:
- Fibroblasts: produce fibres and ground substance of ECM
- Adipocytes: store lipids as an energy source
- Fixed macrophages: phagocytise foreign materials
- Mesenchyme cells: divide to produce new CT
Wanderer:
- Mast cells: release histamine and heparin to produce local inflammation
- Plasma cells: produce antibodies that bind to pathogens
- Free macrophages: phagocytise foreign materials
- Other leukocytes: attack foreign bodies
Areolar CT is the most commonly found CT in the body. It is loose CT proper tissue. What is its function?
Areolar CT wraps around and cushions organs
What is the function of reticular CT?
Reticular CT is meshwork of reticular fibres that form the soft internal skeleton (stoma)
What is the key difference between dense regular CT and dense irregular CT? (in terms of functionality)
Dense regular CT provides strength and flexibility in a single direction; dense irregular CT provides strength in multiple directions
What is apocrine secretion?
Apocrine secretion occurs when vesicles containing secretory product “bud off” the cell
What is the function of muscle?
The function of muscle is to generate motile forces via contraction
Name the two main contractile proteins found in muscle
Actin and Myosin
What is a myofilament and what are the two types of myofilament? What proteins make up each type of myofilament?
Myofilaments are assemblies of actin and myosin.
Thick myofilaments: myosin with myosin globular heads
Thin myofilaments: actin
How do myofilaments generate contraction?
Myosin heads of thick myofilament interact with the actin of thin myofilament
What are myofibrils?
Myofibrils are organelles formed by bundles of myofilaments
What are muscle fibres?
Muscle fibres are muscle ‘cells’ which consist of several myofibrils
What are some features of muscle fibres?
They are large (due to fusion myoblasts during development); they are multinucleated (with nuclei in the peripheries to allow myofibril movement) and they are striated
What are fascicles? What do they make up?
Fascicles are bundles of muscle fibres. Multiple fascicles bundle together to form the whole muscle.
Outline the organisational structure of muscle.
Actin and Myosin -> Myofilaments -> Myofibril -> Muscle Cells -> Fascicles -> Muscle
What are the 3 types of muscle connective tissue? What parts of the muscle do they cover?
Endomysium: surrounds muscle fibres
Perimysium: surrounds fascicles
Epimysium: surrounds whole muscle
What is a sarcomere?
Sarcomeres are the contractile functional units of myofibrils
Explain what A-bands, I-bands, Z-discs and H-zones are. What occurs during contraction?
A-bands: thick myofilaments (dark bands)
I-bands: thin myofilaments (light bands)
Z-discs: an anchoring protein that secure I-bands to cell membrane. Z-discs move closer during contraction.
H-zone: the central region of A-bands that contain no myosin heads
What are the three types of muscle? Where is each type found?
Skeletal: attached to bones to generate movement
Smooth: found in the walls of visceral organs
Cardiac: found in the heart
What are some characteristics of skeletal muscle?
Skeletal muscle is striated (due to presence of sarcomeres); it is under voluntary control; has a high number of mitochondria (high energy requirements); multinucleated
What are some characteristics of smooth muscle?
Smooth muscle is not striated; it is under autonomic control (unconscious); they are uninucleated; look like normal cells and create tension rather than large changes in shape
What are some characteristics of cardiac muscle?
Cardiac muscle has an internal pacemaker that controls contraction (autonomic); majority uninucleated; have a branching structure and contain interpolated discs (similar to gap junctions) that allow a contraction to spread out, creating uni-directional flow
What is the function of Sarcoplamsic Reticulum (SR) and T-Tubules (TT)?
SR and TT release Ca2+ into myofibrils to initiate interaction between myosin heads and actin
In general, what are the differences in function between simple and stratified epithelia?
Simple epithelia are usually to allow secretive and absorption; stratified epithelia usually provide more protection
What are the general functions of squamous, cuboidal and columnar cell types?
Squamous: allow rapid diffusion due to flat nature. Also can be stacked to create protective stratified layers
Cuboidal: cytoplasm volume allows more of a secretory and absorption role
Columnar: large cytoplasmic volume means columnar epithelia play a role in absorption and filtration
Describe the structure of hyaline, fibrocartilage and elastic cartilage (refer to fibres and ECM)
Hyaline: ECM consists of non-collagenous proteins
Fibrocartilage: Strong bundles of collagen present
Elastic: many chondrocytes, ECM is criss-crossed by a dense network of elastic fibres
