Muscle, skin & tissue Flashcards
1
Q
Tissues introduction
A
- Tissues are comprised of cells but in large numbers
- Can be classified according to their cells in terms of size, shape and function
- Four main types (with further sub-divisions)
- Epithelial – ‘protection, secretion, absorption’- line things or coats things either as a protective barrier or to secrete substances like mucus or to absorb substances like in the guts in the digestive system to absorb nutrients.
- Connective – ‘support’- holding things together and giving them shape and substance.
- Muscle – ‘movement’- that we can control such as skeletal muscles which we use to move our limbs. Or involuntary muscle such as in the heart which we don’t actively control.
- Nervous – ‘internal communication’- in our body, communicate from one thing to another.
- ‘Histology’ – study of tissues
2
Q
How Tissues Form
A
- All tissues develop from three primary germ cell layers in an embryo:
- Ectoderm (outer) – nervous, epithelial. (what eventually turns into our nervous tissue and epithelial tissue)
- Mesoderm (middle) – epithelial, muscular (what eventually turns into our muscular tissue and epithelial tissue)
- Endoderm (inner) – epithelial
3
Q
Cellular differentiation
A
- process by which cells gain their specific function/shape to form tissues
- Stem cells- have the potential to become a multiple different type of cells. It is the building block which can be used to make different types of tissues.
- Determination – of a pathway of cell types
- Differentiation – to a specific cell type
4
Q
Morphogenesis
A
– process by which cells/tissues become organised and form structures/organs
* Differentiation of cells into tissue and organisation of systems occurs within 12 weeks of gestation
5
Q
Levels of Organisation
A
Tissues
* Cells which share common aspects of morphology (shape) and function
Organs
* Structures formed from more than one tissue and with specific functions.
Systems
* Organisations of organs and structures which function in a coordinated fashion to fulfil a common goal or goals.
6
Q
Levels of organisation, example: Heart tissue
A
- Different type of cells come together to form a tissue
- Heart made up of muscle, such as an outer protective coating called the pericardium, the internal epithelial layout.
- 3 different types of tissues of the heart which make up the structure, the organ which is the heart.
- The heart works alongside the blood vessels to pump and distribute blood oxygen, carbon dioxide around the body, which makes up our cardiovascular system.
7
Q
Epithelial Tissue (Epithelium)
A
- Covers the body and lines all internal cavities (respiratory system, our gastrointestinal tract, our arteries), tubes and organs
- Also contains certain glands- A gland are a type of cell which produce a substance. For example goblet cells produce mucus (protecting body by lining and making things smooth).
- Tightly packed cells, minimal intercellular ‘matrix’ between them- meaning things can’t pass in between.
- Communicate with the external environment, protect us from them!
- Structure and function closely related:
- Protection (in a range of forms)
- Secretion
- Absorption
Broadly divided into: - Simple – single layer of cells
- Stratified – multiple layers
8
Q
Simple Epithelium
A
- Single layer of cells
- Bound to underlying tissue by basement membrane of connective tissue
- Roles in absorption/secretion rather than protection
- Types according to shape and function – taller in more active tissues
- include squamous, cuboidal and columnar
9
Q
Squamous
A
- Flat cells tightly packed – like paving
- Smooth lining membrane for diffusion
- Examples in blood vessels, collecting ducts of kidney and alveoli in lungs
10
Q
Cuboidal
A
- More actively involved in secretion/absorption processes
- Tubules in kidney and glands such as thyroid
11
Q
Columnar
A
- Contains adapted cells to perform specific functions in secretion/absorption
- Lines range of organs and internal tracts
- Examples include trachea and small bowel
- Adaptions include goblet cells (mucous secretion), microvilli (absorption) and cilia (propulsion of particles)
12
Q
Stratified Epithelium
A
- Layers of cells of various shapes
- Main role is protection of underlying tissues from damage
- New cells in deep layer pushed to surface and shed – continuous process
- Two types:
- Stratified squamous
- Keratinised – contain keratin; tough waterproof protein, e.g. skin
- Non-keratinised – no keratin; prevents drying out of tissues, e.g. conjunctiva of eye, mouth
- Transitional
- More rounded, allows stretching
- Found in urinary tract, e.g. bladder (so it can expand
13
Q
Tissue Membranes
A
- Thin layer or barrier surrounding and separating cells, tissues and organs
- Epithelial
- Forms outer covering of internal and external surfaces
- Layers of epithelium supported by connective tissue
- Three types:
- Mucous
- Serosal
- Skin
- Synovial
- Related to joints and tendons
- Reduces friction between structures
- Areolar (loose connective tissue) and elastic fibres
- Produce synovial fluid – lubricant and source of nutrients to cartilage
14
Q
Mucous Membrane
A
- Often referred to as mucosal layer or mucosa
- Provides a moist, slippery protective barrier/lining
- Goblet cells interspersed within epithelium produce mucous
- Protects, lubricates and captures foreign particles
- Examples include internal tracts/cavities:
- Gastrointestinal tract
- Respiratory tract
- Genitourinary tracts
15
Q
Serous Membrane
A
- Also know as ‘serosa’
- Double layer of areolar (loose) connective tissue with potential space in between
- Epithelial lining of layer produces watery ‘serous’ fluid into space
- Allows layers to glide smoothly over each other and ‘stick together’
- Layers are:
- Visceral – inner layer covering an organ
- Parietal - outer layer covering inside a cavity
- Examples include:
- Pleura – outside of lungs and inside of chest wall (thoracic cavity)
- Peritoneum – outside of abdominal organs and inside of abdominal cavity
16
Q
Nervous Tissue
A
- Brain, spinal cord and nerve
- Communication system for our body
- The nervous system is made of two types of tissue:
- Neurones
- ‘excitable’
- nerve cells
- consist of a cell body (grey matter), an axon, and dendrites (neuron processes - white matter)
- bundles of neurones form nerves
- production and transmission of signals
- cannot divide
- Glial cells
- ‘non-excitable’
- four cell types which support the neurones to do their job
- much more abundant (10x)
- Can divide
17
Q
Connective Tissue
A
- Most prevalent tissue type in body
- Cells more widely spaced – more extracellular matrix
- Matrix of ‘fibres’ which maybe elastic, fatty, spongy, or very tough
- Prominent blood supply to support functions:
- Structural support and anchoring
- Mechanical protection and repair
- Transport/storage of essential substances
- Insulation
- Found in all organs where it supports the specialised functional tissue
Contains cells related to its function, eg. white blood cells (leukocytes), fibroblasts (produce collagen and elastic fibres),
18
Q
Important Proteins
A
- Comprise 50% of organic matter in body
- Chains of amino acids
- Structure of a protein determines function;
- Structural/fibrous proteins – connections, structure and strength of tissues, e.g.
- Collagen – most abundant in body. Connective tissues (including bone, tendons and ligaments)
- Elastin – elastic and flexible. Connective tissues
- Keratin – very strong, water resistant. Hair nails and skin
- Globular/functional – ‘do things’ massive range of vital physiological processes and cell functions
- E.g. antibodies, hormones, enzymes, transport
19
Q
Types of Connective Tissue
A
- Loose (areolar)
- Reticular
- Dense connective
- Fibrous
- Elastic
- Blood – fluid connective tissue
- Bone
- Cartilage
20
Q
Areolar (loose connective)
A
- Relatively loose matrix supported by collagen and elastic fibres
- Disorganised matrix
- Provides elasticity and strength, and support/attachment to other tissues
- Found everywhere, e.g. between the skin and muscles
- Adipose (fatty)
- Loose matrix of connective tissue with adipocytes containing large fat globules
- “fatty tissue”
- Up to 25% of body mass
- Store of energy and insulation
- Found between skin and muscle and supporting organs (protection)
21
Q
Reticular
A
- Comprised of very fine collagen fibres (reticular)
- Interspersed with large numbers of white blood cells
- Related to immune system; found in lymphatic organs
- Dense connective tissue
- More closely packed fibres, fewer other cells
- Organised matrix
- Poorer blood supply
- Fibrous – densely packed collagen fibres in bundles; Tough and strong. e.g. ligaments, periosteum of bone, muscle fascia (sheath) and tendons, covering of organs
- Elastic – elastic fibres allows stretch and recoil. e.g. walls of blood vessels and airways of lung
22
Q
Types of Connective Tissue – Cartilage
A
- Type of connective tissue; firmer than other types
- Chondrocytes (cartilage-cells) lie within varying matrix of collagen and elastic fibres
- Differences between types dependent on this matrix
- More stress/weight-bearing; more collagen, less flexible
- Avascular; vascular supply via diffusion from other tissues
- Three functions:
- Provide support/strength
- Smooth, reduced friction surface at joints
- Involved in development/growth of bones (eg physeal plates)
- Normally invisible on X-ray unless abnormal (same for all connective tissues)
23
Q
Hyaline (articular) cartilage
A
- Groups (nests) of chondrocytes in a solid/dense matrix
- Very smooth and blue/white in appearance
- Low friction
- Predominantly found:
- End of long bones in synovial/cartilaginous joints Costal cartilage joining ribs to sternum
- Forms part of the larynx, trachea, and bronchi
24
Q
Fibrocartilage
A
- Dense groups of inelastic collagen fibres interspersed with chondrocytes
- Very tough, slightly flexible connective tissue
- Predominantly found:
- Intervertebral discs
- Meniscus of the knee
- Rim of shoulder/hip joints; called a labrum- help increase strength of limbs
25
Q
Elastic fibrocartilage
A
- Not associated with joints
- Chondrocytes lie within solid matrix of elastic fibres
- Flexible tissue providing shape/support
- Predominantly found in:
- Pinna (lobe of ear)
- Epiglottis
- Tunica media (wall) of blood vessels
26
Q
Types of connective tissue – skeletal system
A
- Important in understanding the structure and function of the musculoskeletal system in particular
- Skeletal Muscle; movement/joint stabilisation
- Fibrous tissue; forms joint capsule, muscle fascia and tendons
- Tendon; continuation of muscle into bone, transmission of forces
- Ligament; binds bones together for stability. Dense fibrous connective tissue
- Cartilage:
- Hyaline
- Fibrocartilage
- Elastic
27
Q
Muscle
A
- Structure allows contraction and relaxation of fibres
- Movement – either of body or within body
- Some voluntary, some involuntary
- Requires oxygen and fuel (predominantly glucose) to function
- Different contractible cells (fibres) dependent on three types:
- Smooth
- Cardiac
- Skeletal
28
Q
Smooth Muscle
A
- Not controlled voluntarily, autonomic/hormone control – involuntary
- Spindle shape fibres with central nucleus, does not have stripes (striations) in fibres – non-striated
- Related to movement within hollow organs/movement through body – visceral
- Layers of fibres forming sheets of muscle
- Functions include:
- Propulsion (peristalsis) – e.g. gastrointestinal tract, ureters
- Excretion - e.g. bladder
- Dilation/constriction – walls of blood vessels (role in blood pressure)
29
Q
Cardiac Muscle
A
- Found only in the heart
- Not controlled voluntarily – involuntary
- Autonomic nervous system and hormones supporting internal nerve stimulation (pacemaker)
- Fibres are striated/ striped
- Each fibre has a central nucleus and ‘branches’
- Ends/branches connected by ‘intercalated discs’ or joints
- Fibres stimulated from one to next (conduction/spread), not individually
30
Q
Skeletal Muscle
A
- So called as related to movement of the skeleton
- Is under ‘conscious’ control – voluntary
- Has transverse stripes across fibres – striated
- Each cell/fibre can be very long and contains several nuclei
- Arranged in bundles (fascicles) surrounded by dense connective tissue (fascia)
- Stimulated by impulses from motor nerves in brain/spinal cord
31
Q
Skeletal Muscle – gross structure
A
- Each muscle is comprised of many tens of thousand of individual fibres
- Supported by blood vessels and nerves and extensive dense connective tissue (fascia)
- From small to large:
- Individual fibres surrounded by endomysium
- Grouped into bundles called fascicles and surrounded by perimysium
- Whole muscle encapsulated by epimysium
- Fascia extends to both ends of muscle and directly connects to bone as either:
- Tendon – more like a rope
- Aponeurosis – flat sheet
- Transmit force of muscle to points of attachment on skeleton
32
Q
Skeletal Muscle – microscopic structure
A
- Parallel dark thick (myosin) and light thin (actin) filaments run along length of muscle fibres
- Each ‘unit’ of bands know as sarcomere
- These filaments in the cytoplasm (sarcoplasm) of muscle cells run parallel to muscle fibre and are ‘contractile’
- Several nuclei due to size of cells
- Multiple mitochondria to convert oxygen/glucose to ATP (adenosine triphosphate) for energy
- Oxygen and calcium essential nutrients for muscle action so are stored in large supplies in muscle
33
Q
Skeletal Muscle – Contraction
A
- Stimulation of muscle fibres occurs at the neuromuscular junction
- This signal is sent through channels between muscle cells
- Causes calcium to be released from the muscle cell and causes the adjacent mysosin and actin sections to ‘bind’ together
- ATP provides energy for two to slide over each other, shortening the sarcomere
- When occurs over large numbers of fibres, muscle contracts
- Removal of nerve stimulus causes calcium to be reabsorbed, breaking bond between myosin and actin, and return to original position
34
Q
Effects on Skeletal Muscle
A
- Performance – regular training (especially anaerobic) increases muscle increases the size of muscle fibres
- Muscle fatigue – occurs when demand of oxygen and glucose (fuel) is exceeded. Causes anaerobic process to take over which release lactic acid. Takes time to recover supplies and repair damage.
- Muscle tone – to prevent muscle fatigue when maintaining posture, muscle fibres activated in groups for short periods of time
35
Q
Skeletal muscle – actions
A
- Effect of muscle contraction is force transmitted through tendons to bone
- Must be attached at both ends
- Usually arranged in antagonistic pairs
- Muscle groups arranged to work together but in opposition during movement
- Isotonic movement – increase in muscle contraction/tension to provide movement
- Isometric movement – increase in muscle contraction/tension with no movement
36
Q
Naming Muscles
A
- Named in a range of ways related to:
- Direction of muscle fibres, e.g transversus abdominus
- Shape, e.g deltoid
- Position of muscle in relation to other anatomy, e.g. tibialis anterior
- Movement it produces, e.g. flexor digitorum
- Number of attachment sites, e.g biceps brachii
- What bone it is connected to, e.g. frontalis
Origin - Usually more proximal attachment
- Stays in place on contraction
Insertion - Usually more distal attachment
- Moves on contraction
37
Q
Integumentary system
A
Whole body covering”
Functions:
* Protect the body’s systems
* Maintain temperature
* Provide sensory information on the environment; e.g touch
* Excretion and absorption
* Synthesis of vitamin D
* Define personal appearances
Consists of:
* skin
* hair /nails
* accessory glands; e.g. sweat / sebaceous
* Supporting muscles / nerves
38
Q
Why is the Skin Important in Radiography?
A
- Skin erythema has a threshold dose above which they are likely to occur
- Hair loss and erythema have been reported during prolonged scanning e.g CT brain perfusion studies and image-guided interventions
- Skin damage can be caused by cumulative dose from multiple diagnostic procedures
- Can be mistaken for allergic reactions to defibrillator pads or electrodes
39
Q
The Skin – Overview
A
- Largest body organ; average 2 square metres and 5kg (about 16%)
- Made up of different tissues with varying functions
- Ranges in thickness from 0.5mm (eyelids) to 4mm (calcaneum); average 1-2mm
- Continuous with mucosa from respiratory, digestive, urogenital systems and eyes
- Two main parts:
- Epidermis; superficial, thinner, epithelial
- Dermis; deeper, thicker, connective tissue
- Hypodermis/subcutaneous layer;
- areolar and adipose tissue
- connected to dermis and underlying tissue via connective fibres
- Storage for fat and blood vessels to skin
- Sensitive to pressure due to nerve endings (corpuscles of touch)
40
Q
Epidermis
A
- Stratified squamous epithelium
- Contains keratin (also found in hair/nails),
- insoluble tough, fibrous protein
- Protects tissues from heat, microbes, and chemicals
- Made up of four cell types:
- Keratinocytes; 90% - produce keratin and lamellar granules (waterproofing)
- Melanocytes; 8% - produce melanin granules for keratinocytes and other cells; pigment to absorb UV light and shield cell DNA. Give skin colour
- Langerhan’s cells; from red bone marrow – immune response to microbes
- Merkel cells; in deepest layer – contact with sensory neurons for touch sense
- Keratinisation:
- Process of new cells in basale layer migrating to superficial layers
- Normal organelles replaced by keratin as cells apoptoses
- Takes 4 weeks in total
- 4 layers generally; ~1mm thick
41
Q
Dermis
A
- Deeper layer of skin; connective tissue of collagen and elastic fibres
- Also contains:
- Fibroblasts, macrophages, adipocytes
- Neurovascular structures
- Sebaceous and sweat glands
- Hair follicles
42
Q
Accessory Structures
A
- Hair
- Glands:
- Sebaceous
- Sudoriferous Ceruminous
- Mammary
- Nails
43
Q
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