CTL Week 1-5

CTL

Describe the key elements of the cell theory

All organisms are composed of cells, cells are the basic structural and organisational unit of all living organisms and cells can only form from other cells

Compare and contrast the features of prokaryotic and eukaryotic cells

Eukaryotic cells have a nucleus (linear DNA) and membrane-bound organelles while prokaryotic cells do not have a nucleus (DNA flows freely in the cytoplasm in circular form) and lack the organisation of the cytoplasm into organelles.

What is an organelle?

Membrane-bound structures which carry out specific functions within the cell.

List the essential functions of life, and the requirements to support these

Metabolism, excretion, digestion, responsiveness, movement, growth, reproduction, maintaining boundaries.
Homeostasis, atmospheric pressure, temperature regulation, water and nutrients are some of the requirements to support the essential functions of life.

Outline the structural levels of organisation of the human body

Chemical, cellular, tissue, organ, organ system, organismal.

Explain, with examples, how structure and function are related

Structure and function are related because organisms must enact specific functions such as respiration in order to live so the structure must support this function such as the lungs being able to expand to allow air to enter inside the body as oxygen and exit outside of the body as carbon dioxide.

Explain the principle of homeostasis

Homeostasis is the ability of the body to maintain a constant internal environmental in an ever-changing external environment.

Describe the basic components of a homeostatic negative feedback system

A homeostatic negative feedback system works to decrease an imbalance and return the body to a balanced condition (homeostasis). The basic components of a homeostatic negative feedback system include a stimulus, receptor, control centre and effector.

Explain how imbalances in homeostasis are related to disorders

Homeostasis is the ability of an organism to maintain a balanced internal environment, however if an imbalance occurs the body cannot perform its usual function leading to a disorder. For example, if a person has the disorder anorexia, they will not be able to eat enough to maintain a balanced state of nutrient intake and thus will become malnourished.

Tissue

A group of cells and the material surrounding them, that work together to perform a particular function.

Organ

A collection of tissues that carry out a specialised function of the body

Describe the three main features of cells and their functions

Plasma/ cell membrane- barrier
Cytoplasm- intracellular solution
Nucleus- control centre

Describe the structure of the plasma membrane and the fluid mosaic model

The structure of the plasma membrane is a lipid bilayer. Lipids are amphipathic molecules meaning they have both polar and non-polar elements. In the plasma membrane the phosphate 'head' is polar and is hydrophilic while the fatty acid 'tails' are nonpolar and are hydrophobic. The lipid bilayer is mainly made up of phospholipids but also contains cholesterol and glycoproteins. The fluid mosaic model presents the idea that the lipid bilayer is a 'lipid sea' with icebergs (peripheral proteins) and islands (integral proteins).

Describe the various functions of the plasma membrane

Selective permeability, flexibility and communication.

Microvilli

'Finger-like' extensions which increase surface area and cannot move. Specialised for absorption- e.g. kidneys and digestive tract.

Villi

'Finger-like' extensions which increase surface area and cannot move. Only found in the small intestine.

Flagella

Whip-like structure, mobile (move from one place to another), only sperm have them in humans

Endoplasmic Reticulum (ER)

Smooth ER: network of membrane tubules which contain enzymes that synthesise fatty acids and steroids and help inactive and detoxify lipid-soluble drugs
Rough ER: folded into a series of flattened sacs, studded with ribosomes which synthesises glycoproteins and phospholipids
Funcions: synthesis, transport and storage

Golgi Complex

Consist of 3-20 cisternae (small, flattened membranous sacs with bulging edges), modifies, sort and packages proteins for secretion

Ribosomes

Consist of a large subunit and a small subunit, synthesise proteins

Lysosomes

Membrane-enclosed vesicles which have powerful enzymes that can break down molecules, can initiate autophagy (eating of damaged organelles) or autolysis (eating of cell itself when it is no longer performing its correct function)

Mitochondria

Inner mitochondrial membrane contains folds called cristae which increase surface area, are the 'powerhouse' of the cell because they generate most of the cellular energy (ATP) through aerobic respiration

List the major structural components of the nucleus and describe the major functions of the nucleus

Control centre of the cell
DNA is replicated, and RNA is synthesised.
Nucleolus- spherical structure in the centre which is where ribosomes are synthesised.
Nuclear envelope- lipid bilayer similar to the plasma membrane and nuclear pores which are large and allow ribosomes to exit from the nucleus into the cytoplasm.

Outline the events and processes involved in cell division and the cell cycle

The cell cycle is an orderly sequence of events in which a cell duplicates its contents and divides into two. Cell division begins with interphase. Interphase has three sub-phases: G1 phase (replication of organelles and cytosolic components), S phase (where DNA replication occurs) G2 phase (cell growth continues, and other proteins are synthesised in preparation for cell division- at the end there is a G2 checkpoint which ensures that all DNA has been replicated).

Cytoplasm

The material within a cell, excluding the nucleus.

Cytosol

Fluid portion of cytoplasm thats sourrounds organelles.

Cilia

Short, hair-like projections that extend from the surface of the cell, are motile (move on the spot), move fluids along a cell's surface

Microfilaments

Thinnest elements of the cytoskeleton.
Composed of the proteins actin and myosin and are most prevalent at the edge of a cell.
Function: help generate movement and provide mechanical support.

Intermediate filaments

Thicker than microfilaments but thinner than microtubules. Several different proteins can compose intermediate filaments, which are exceptionally strong. They are found in parts of cells subject to mechanical stress; they help stabilise the position of organelles such as the nucleus and help attach cells to one another.

Microtubules

Largest of the cytoskeletal components
Long, unbranched hollow tubes composed mainly of the protein tubulin. The assembly of microtubules begins in an organelle called the centrosome. The microtubules grow outward from the centrosome towards the periphery of the cell. Microtubules help determine cell shape. They also function in the movement of organelles such as secretory vesicles, of chromosomes during cell division, and of specialised cell projections, such as cilia and flagella

Cytoskeleton

Network of protein filaments that extends throughout the cytosol.
Three types of filaments contribute to the cytoskeleton's structure.

Distinguish the major events of, and the and difference between mitosis and meiosis.

• Mitosis
INTERPHASE \---\> Prophase (chromatin condenses into chromosomes), Metaphase (chromosomes align along the metaphase plate through action of the mitotic spindle), Anaphase (chromosomes separate), Telophase (chromosomes relax), Cytokinesis (cell splits)
• Meiosis I
INTERPHASE \---\>Prophase (chromatin condenses into chromosomes, CROSSING OVER OCCURS), Metaphase (chromosomes align through action of the mitotic spindle), Anaphase (chromosomes separate), Telophase (chromosomes relax), Cytokinesis (cells split into two haploid cells)
• Meiosis II
Prophase (chromatin condenses into chromosomes), Metaphase (chromosomes align through action of the mitotic spindle), Anaphase (chromosomes separate), Telophase (chromosomes relax), Cytokinesis (cells split into four haploid cells)

The main differences between mitosis and meiosis is that in meiosis, crossing over of chromosomes occurs in prophase in meiosis I and there are two stages because meiosis produces haploid (germ cells) while meiosis produces diploid (somatic cells).

Exocytosis

Process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.

Endocytosis

The taking in of matter by a living cell by invagination of its membrane to form a vacuole.

Outline the characteristics of the four basic types of tissues that make up the human body

Nervous- maintains homeostasis by generating electrical signals
Connective- protects and supports the body and its organs
Epithelial- covers body surfaces
Muscular- specialised for contraction and generation of force

Describe the cell shapes and arrangements seen in epithelial tissue

Epithelial tissue has closely packed cells which are cuboidal, squamous and columnar in shape. There is an apical (top) surface and basal (bottom surface). The basal surface is on top of the basement membrane which has two layers. The top layer is the basal lamina (which has glycoproteins, proteoglycans, lamina and collagen) and the bottom is the reticular lamina (which has collagen produced by connective tissue cells called fibroblasts). The lateral surfaces are the middle surfaces in between the apical and basal surfaces. Epithelial tissue is situated above connective tissue.

Simple squamous epithelium

'COVERING AND LINING' AND 'SECRETION'
Structure:
Single layer of flattened cells

Function:
Allows materials to pass through by diffusion and filtration and secretes lubricating substance

Location:
*Most commonly lines the cardiovascular & lymphatic system (heart, blood vessels,
lymphatic vessel linings) - Endothelium

*Forms the epithelial layer of serous membranes (peritoneum, pleura, pericardium) - Mesothelium

*Also found in air sacs of lungs, glomerular (Bowman's) capsule of kidneys, inner surface of
tympanic membrane (eardrum);
NOT found in areas subject to wear and tear; LUNG AIR SACS

Simple cuboidal epithelium

'SECRETION AND ABSORPTION'
Structure:
Cube-shaped or hexagon-shaped, one layer

Function:
Secretion and absorption

Location:
Covers surface of ovary; lines anterior surface of capsule lens of the eye; lines kidney tubules and smaller ducts of many glands; makes up secreting portion of some glands such as thyroid gland and ducts of pancreas; PANCREAS

Simple columnar epithelium

'SECRETION AND ABSORPTION'
*Non-ciliated and ciliated

Structure:
Rectangular, one layer, nucleus is in one line

Function: Secretion and absorption, have goblet cells- modified columnar epithelial cells that secrete mucus at their apical surfaces

Location:
NON-CILIATED (has microvilli):
Lines gastrointestinal tract (from stomach- helps prevent destruction of stomach lining by acidic gastric juice secreted- to anus), gall bladder; digestive, respiratory, reproductive and urinary tracts; DUODENUM
CILIATED (movement):
Lines some bronchioles (small tubes) of respiratory tract, uterine (fallopian) tubes, uterus, some paranasal sinuses, central canal of spinal cord, and ventricles of brain

Pseudostratified columnar epithelium

'COVERING AND LINING' and 'SECRETION AND ABSORPTION'
*Non-ciliated and ciliated

Structure:
Looks like stratified but has cells of different heights, 'fake' stratified
NON-CILIATED:
Lacks goblet cells
CILATED:
Have goblet cells

Function:
NON-CILIATED: Absorption and protection
CILIATED:
Secretes mucus, ciliated tissue moves mucus

Location:
NON-CILIATED:
Epididymis, part of male urethra
CILIATED:
Airways of most of upper respiratory tract (trachea)
*TRACHEA

Stratified squamous epithelium

'COVERING AND LINING'
*Keratinised and non-keratinised

Structure:
Two or more layers, cells in apical layer and several layers deep to it are squamous; cells in deeper layers vary from cuboidal to columnar

Function:
Protects against abrasion, water loss, ultraviolet radiation and foreign invasion

Location:
KERATINISED:
Develops tough layer of keratin in apical layer of cells and several layers deep to it; forms superficial layer of the skin
*SKIN OF THE EAR
NON-KERATINISED:
Constantly moistened by mucous from salivary and mucous glands; lines wet surfaces (lining of mouth, oesophagus, part of epiglottis, part of pharynx and vagina) and covers tongue;
*VAGINA

Stratified cuboidal epithelium

'COVERING AND LINING' AND 'SECRETION AND ABSORPTION'
Structure:
Cube-shaped or hexagon-shaped, layers

Function:
Protective tissue; limited secretion and absorption

Location:
Rare, ducts of adult sweat glands and oesophageal glands, part of male urethra

Stratified columnar epithelium

'COVERING AND LINING' AND 'SECRETION'
Structure:
Rectangular, layers, basal layers usually consist of shortened, irregularly shaped cells; only apical layer has columnar cells

Function:
Protection and secretion

Location:
Uncommon, lines part of urethra; large excretory ducts of some glands, such as oesophageal glands, small areas in anal mucous membrane, part of conjunctiva of eye

Transitional epithelium

'COVERING AND LINING'
Structure:
Smaller cells transitioning to bigger cells;
looks like stratified cuboidal epithelium, except apical layer tends to be large and rounded; as tissue is stretched, cells become flatter, giving the appearance of stratified squamous epithelium

Function:
Multiple layers and elasticity make it ideal for lining hollow structures (urinary bladder); expansion and stretching

Location:
Lines urinary bladder and portions of ureters and urethra

Describe the structural classification of exocrine glands and identify the different types of multicellular exocrine glands

Exocrine glands can be unicellular (goblet or mucous cells) or multicellular (sweat, oil and salivary glands).
Multicellular glands can be further classified as having either a compound or simple duct or a branched, coiled, tubular (straight), acinar/ alveolar (rounded) or tubuloacinar (both straight and rounded) secretory units.

Merocrine

- Merocrine gland secretions are synthesised on ribosomes attached to Rough ER
- Processed, sorted, and packaged by the Golgi complex; released from the cell in secretory vesicles via
exocytosis
- Most exocrine glands of the body are merocrine glands.
E.g.; salivary glands & pancreas

Apocrine

- Apocrine glands accumulate their secretory product at the apical surface of the secreting cell
- Later that portion of the cell pinches off by exocytosis from the rest of the cell to release the secretion.
The cell repairs itself and repeats the process
- E.g.; secretion of milk fats in the mammary glands

Holocrine

- Holocrine gland cells accumulate a secretory product in their cytosol. As the secretory cell matures, it
ruptures and becomes the secretory product
- Because the cell ruptures in this mode of secretion, the secretion contains large amounts of lipids from the
plasma membrane and intracellular membranes. The sloughed off cell is replaced by a new cell
- E.g.; Sebaceous gland of the skin

Tight Junctions

(Zona Occludens)
Web-like strands of transmembrane proteins (occludins and caludins); seal off passage ways
*Abundant in cells of epithelial tissue that lines the stomach, intestines, testis & urinary
bladder

Adherens Junction

(Zona Adherens)
Contains proteins: plaque and cadherins; adhesion belts; prevent separation
*Help epithelial surfaces resist separation during various contractile activities (e.g.
intestine)

Hemidesmosomes

Do not link to adjacent cells but anchor cells to the basement membrane; integrins (transmembrane glycoproteins) attach to intermediate filaments which contain the protein keratin on the inside of the plasma membrane and attach to laminin on the outside of the plasma membrane
*They anchor cells to the basement membrane.

Desmosome

(Macula Adherens)
Contain plaque and cadherins (transmembrane glycoprotein); attach to intermediate filaments which contain the protein keratin; prevent separation
*Common among the cells that make up the epidermis and cardiac muscle cells

Gap Junction

(Nexus)
Membrane proteins called connexins form tunnels called connexons (connect neighbouring cells), transfer ions and small molecules
*Found in many areas of the body including epithelia, which are the coverings of body surfaces, as well as nerves, cardiac (heart) muscle, and smooth muscle (such as that of the intestines).

Compare the features of epithelial and connective tissue

Epithelial tissue has many cells tightly packed together with little or no extracellular matrix and does not have blood vessels while connective tissue has scattered cells and therefore a lot of extracellular matrix and has blood vessels present.

Histological section names

Transverse: horizontal
Oblique: diagonal
Longitudinal: vertical (longest axis)

Heart serous membrane

Percardium

Lungs and thoracic wall serous membrane

Pleura

Abdominopelvic cavity and viscera (organs) serous membrane

Peritoneum

3 types of epithelial membranes

Cutaneous (skin): exposed, protection
Serous: internal, reduces friction
Mucosa: secretes mucus, lines many body cavities and organs

Viseral layer of serous membrane

Inner layer of serous membrane that adheres to the inner organ

Pareital layer of serous membrane

Outer layer of serous membrane that adheres to the outer organ

Connective tissue proper types

Loose connective tissue:
Relatively fewer cells and fibers than in dense connective tissue; fibers are loosely arranged (areolar, adipose, reticular)

Dense connective tissue:
Higher proportion of fibers to ground substance; protein fibers are densely packed together (dense regular, dense irregular, elastic)

Areolar connective tissue

Structure: Contain fibroblasts, not many collagen and elastic fibers, viscous ground substance
Function: Binds and packs around organs
Location: Around nearly every body structure (packing material of the body), subcutaneous (deep) and papillary (superficial) skin, lamina propria of mucous membranes, around blood vessels, nerves and body organs

Adipose connective tissue

Structure: Contain adipocytes

Function: Protects, stores fats, insulates (prevents heat loss)

Location: Subcutaneous (deep) layer of the skin, around the heart and kidneys, yellow bone marrow, padding around joints and behind eyeball in eye socket

*In adults most adipose tissue is white adipose tissue (secretes bioactive peptides called adipokines)
*Brown adipose tissue (BAT) is darker due to very rich blood supply and numerous pigmented mitochondria that participate in aerobic cellular respiration. BAT is widespread in the foetus and infant, adults only have small amounts.

Reticular connective tissue

Structure: Meshwork of reticular fibres

Function: Forms stroma of lymphatic organs

Location: Stroma of liver, spleen, lymph nodes, red bone marrow, reticular lamina of basement membrane, around blood vessels and muscles

Dense regular connective tissue

Structure: Densely packed collagen fibers

Function: Strength and flexibility in a single direction; withstands pulling (tension) along long axis of fibers

Location: Tendons (attach muscle to bone) and ligaments (attach bone to bone)

Dense irregular connective tissue

Structure: Densely packed collagen fibers are interwoven; fibers are irregularly clumped together and project in all directions

Function: Tensile strength in all directions

Location: Occur in sheets such as FASCIAE (tissue beneath skin and around muscles and other organs), reticular (deeper region) of dermis of skin, fibrous pericardium of heart, periosteum of bone, perichondrium of cartilage, joint capsules, membrane capsules around various organs, also in heart valves

Elastic connective tissue

Structure: Elastic and collagen fibers are arranged irregularly

Function: Provides framework and supports organs, allows for stretching; is strong and can RECOIL to original shape after
being stretched

Location: Walls of large arteries (aorta and vena cava), lung tissue, trachea, bronchial tubes, true vocal chords, suspensory ligaments of penis, some ligaments between vertebrae

Supporting connective tissue types

Cartilage and bone

Cartilage

Abundant extracellular matrix produced by scattered chondrocytes contained in lacuna.
Dense network of collagen fibers and elastic fibers firmly embedded in chondroitin sulphate.
Has few cells and large quantities of ECM.
No nerves or blood vessels in its ECM.
Three types: hyaline, fibrocartilage and elastic

Hyaline cartilage

Structure: Prominent chondrocytes found in lacunae surrounded by perichondrium (connective tissue that envelops cartilage where it is not a joint)

Function: Flexibility and support (weakest type of cartilage)

Location: Nose, ends of long bones, trachea

Fibrocartilage

Structure: Has chondrocytes among clearly visible thick bundles of collagen fibres (no perichondrium because it is already strong)

Function: Support, strength, rigidity (strongest type of cartilage)

Location: Intervertebral discs, menisci (cartilage pads) of knee

Elastic cartilage

Structure: Has chondrocytes in a threadlike, crisscross network of elastic fibers, has a perichondrium (connective tissue that envelops cartilage where it is not a joint)
Function: Strength, elasticity, maintains shape
Location: Auricle of ear

Bone

Stores calcium & phosphorus, red bone marrow (produces blood cells) and yellow bone marrow (a storage site for triglycerides); calcium phosphate makes up 65% of bone weight
Rigid, extracellular matrix takes the form of needle-like crystalline mineral salts called hydroxyapatite
Two types: compact and spongy

Compact bone

Structure: Osteon (or Haversian system), consists of an osteocyte with canaliculi projecting from the centre, which provide transport routes to the osteocytes (surrounded by lacunae), has a central canal/ Haversian canal which contains blood vessels and nerves

Function: -Stores calcium, phosphorous and bone marrow
-Provide support, protection and enable movement


Location: All over the body (skeleton)

Spongy bone

Structure: Consist of thin columns called trabeculae, highly vascularised, increased surface area because of concentric rings (lamellae)

Function: -Stores calcium, phosphorous and bone marrow
-Provide support, protection and enable movement

Location: Found in long bones and surrounded by compact bone tissue

Relate the structures of the connective tissue sub-classifications "bone" and "cartilage" to their functions within the body and their relationship to one another.

Bone and cartilage have very similar structures because cartilage is the precursor to bone (the embryo is made up of cartilage).

Outline the characteristics of structural origin of the "connective tissue" class of tissues

Connective tissue cells are all derived from the same embryological origin which is the embryonic mesoderm (mesenchyme connective tissue).

Extracellular matrix fibers

Collagen fibers, elastic fibers, reticular fibers

Connective tissue cells

Active (-blast), proliferating
Inactive (-cyte)
Resident cells: fibroblasts, adipocytes, fixed macrophages, messenchymal cells
Wandering cells: mast cells, plasma cells, free macrophages, other leukocytes

Fibroblasts

Structure: abundant, large, relatively flat cells, often with tapered ends
Function: produce fibers and ground substance of the extracellular matrix

Adipocytes

Structure: Fat cells with a single large lipid droplet; cellular components pushed to one side
Function: Store lipid reserves

Fixed macrophages

Structure: Large cells derived from monocytes in blood; reside in extracellular matrix after leaving the blood
Function: phagocytise foreign materials

Mesenchymal cells

Structure: Spindle-shaped or stellate (star-shaped) embryonic stem cells
Function: Divide in response to injury to produce new connective tissue cells

Mast cells

Structure: Small cells with a granule-filled cytoplasm
Function: Release histamine to stimulate local inflammation

Plasma cells

Structure: Small cells with a distinct nucleus derived from activated B-lymphocytes
Function: Form antibodies that bind to foreign substances, bacteria, viruses

Free macrophages

Structure: Mobile phagocytic cells formed from monocytes of the blood
Function: Phagocytise foreign materials

Leukocytes

Eosinophils: Migrate to sites of infection (cause inflammation); neutrophils: destroy microbes (like bacteria) by phagocytosis

Skeletal muscle

Structure: Striated, cylindrical, multinucleated, peripherally located nuclei

Function: Heat production, posture and motion

Location: Attached to bone by tendons

Cardiac muscle

Structure: Branched, striated, intercalated discs (contain desmosomes and gap junctions which strengthen, hold fibres together and allow for communication of electrical signals), cardiac myocytes, usually one centrally located nucleus

Function: Pumps blood to all body parts

Location: Wall of the heart

Smooth muscle

Structure: Spindle-shaped, non-striated, single centrally located nucleus, caveloae (sequester and release Ca+ ions- functionally analogous to sarcoplasmic reticulum in skeletal muscle), dense bodies (similar to Z discs of striated muscle)

Function: Motion, constriction, propulsion and contraction

Location: Uterine walls, blood vessel walls, urinary bladder, gall bladder, iris, airways to lungs

Difference between types of muscle tissue

Skeletal
• More structured than smooth tissue
Cardiac
• The nucleus is generally larger than skeletal, endomysium is more limited
Smooth
• No striations because actin and myosin are scattered (have dense bodies (homologus to Z disc)- cytoskeletal components which wrap around the cell like a net)

Endomysium

'Skin' of a myofibril (loose retcular CT)

Perimysium

'Skin' of a fascicle (dense irregular CT)

Epimysium

'Skin' around muscle (dense irregular CT)

Sarcoplasmic reticulum

Fluid-filled membrane that encircles each myofibril, stores Ca+

Myofibril

Made up of myofilaments actin (thin) and myosin (thick) which are contraction proteins; the structural and functional subunits of a muscle fibre and is the contractile
organelle

Muscle fibre

Group of myofibrils is a muscle fibre

Transverse (T) tubules

Extensions of the cell membrane (sarcolemma) that tunnel in from the surface towards the centre of each muscle fibre (provide strength)

Triad

Tubule with 2 terminal cisterns (dilated end sacs of the sarcoplasmic reticulum which surround the T tubules) surrounding it. The function of the triad is to cause calcium flow into the cytoplasm and to initiate muscle contraction