L1a - Tissues & Systems (1) Flashcards
What is an organum?
An instrument or tool
Define ‘Viscus’ / ‘Viscera’ (plural).
Two or more tissues which together perform a specialised function.
How many organ systems are there?
11
What are the 2 different types of tissue?
- Main tissue
- Sporadic tissue
Name the 11 organ systems.
- Integumentary System
- Musculoskeletal System
- Nervous System
- Endocrine System
- Cardiovascular System
- Lymphatic System
- Respiratory System
- Urinary System
- Digestive System
- Reproductive System
- Immune System
Describe the characteristics of tissues.
- Group of similar cells
- Similar embryological origin
- Specialised for a particular function
What are cells separated by?
A matrix
What is a matrix?
Non-living, intercellular material produced by cells
What is the study of tissues called?
Histology
Name the 4 main types of tissues.
- Epithelial Tissue
- Connective Tissue
- Muscle Tissue
- Nervous Tissue
Describe the role of epithelial tissue.
- Protection
- Lining
- Secretion
- Filtration
- Absorption
Describe the role of connective tissue.
- Protection
- Support and binding
- Energy storage
- Transport
- Immunity
Describe the role of muscle tissue.
- Locomotion
- Movement of food
- Beating of the heart
Describe the role of nervous tissue.
- Transmission of impulses to achieve communication, coordination and control
What are epithelial cells closely packed into?
Single continuous sheets or in multiple layers
What do junctions between epithelial cells ensure?
Attachment to neighbouring cells
How can substances pass through epithelial cell layers?
- Diffusion
- Transportation
Epithelial cells are polar. Which 2 surfaces does this result in?
- Apical surface (top)
- Basal surface (bottom)
Describe the apical surface of epithelial cells.
- Exposed to a body cavity
- Line an organ
- Exposed to exterior
- Can contain microvilli or cilia
Describe the basal surface of epithelial cells.
- Attached to a basement membrane secreted by the cells
- Adheres the tissue firmly to nearby connective tissue
What does it mean that epithelia are avascular?
Blood vessels tend to run under epithelial layers, but do not go through them; so rely on diffusion for oxygen and nutrients, and to remove waste.
Capillaries usually found below basement membrane.
Epithelia usually have a _____ supply.
Epithelia usually have a nerve supply.
Epithelia are usually able to __________ via _______ as they often suffer wear and tear.
Epithelia are usually able to regenerate via mitosis as they often suffer wear and tear.
In addition to protection, lining, secretion, filtration and absorption, what else does epithelial tissue function include?
- Lubrication
- Digestion
- Excretion
- Transportation
- Sensory reception and reproduction
What are the three classifications of epithelial cells based on layers?
- Simple (single layer of cells)
- Stratified (multiple layers of cells)
- Pseudo-stratified (look like multiple layers of cells, but only a single layer in reality)
Provide an example of where you may see a simple epithelial cell. Why would this cell type be present here?
- Alveoli of lungs
- Endothelium of blood vessels
- Require fast, seamless diffusion of substances
State the 4 different shapes of epithelial cells.
- Squamous
- Cuboidal
- Columnar
- Transitional
Describe the characteristics of squamous epithelial cells.
- Flat cells
- Oval nuclei
- Thin for diffusion
Describe the characteristics of cuboidal epithelial cells.
- Cube like cells
- Central nuclei
- Can product secretions
- Can participate in absorption
Describe the characteristics of columnar epithelial cells.
- Column shaped cells
- Variable nuclei
- Protect underlying tissue
- Involved in secretion / absorption
Describe the characteristics of transitional epithelial cells.
- Variable shape
- Can change from flat to columnar in response to distension, expansion or movement of body parts
Provide an example of where you may see a stratified epithelial cell. Why would this cell type be present here?
- Skin
- Oesophagus
- Areas exposed to chemical or physical stresses
- Require multiple layers of protection
Provide an example of where you may see a pseudo stratified epithelial cell. Why would this cell type be present here?
- Upper airways
- Trachea
- Bronchi
- Appearance is primarily due to variations in shape and position of the nuclei of its different cell types
Describe a simple epithelium.
Single layer allowing diffusion osmosis filtration secretion and absorption to take place
Describe a stratified epithelium.
Multiple layers of cells protecting deep layers from wear and tear
Describe a pseudo stratified epithelium.
Single layer of cells that appears to consist of multiple layers as they have nuclei at different levels - not all cells reach the surface
Some cells are ciliated or secrete mucus (goblet cells)
What is an integumentum?
A covering
What does the integumentary system comprise?
The skin and its derived organs (hair, glands, nails and nerve endings)
What is the study of skin known as?
Dermatology
The skin is a very large organ. Approximately how many m^2 is the integumentary system?
1.5 - 2 m^2
The skin is a very large organ. Approximately how many mm thick is the integumentary system?
2 - 3mm
The skin is a very large organ. How much does the integumentary system weigh on average?
5 kgs
The integumentary system is the largest _____ organ in the body.
The integumentary system is the largest sense organ in the body.
What are the functions of the integumentary system?
- Protection (external body covering)
- Sensation (temperature regulation)
- Excretion (protection, immunity and resistance)
- Blood Reservoir (synthesis of vitamin D)
What types of cells make up the epidermis?
Stratified squamous
What makes up the dermis?
Primarily, dense irregular connective tissue
What makes up the subcutaneous layer?
Areolar and adipose tissue
Is the subcutaneous layer part of the integumentary system?
No, but it is closely involved with the structure and function of skin.
State some epidermal derivatives.
- Nails
- Hair
- Exocrine glands
What is the role of the dermal papilla?
Receptors for gathering sensory information
What is the role of the arrector pili muscle?
Smooth muscle which is activated by cold or emotional response (contraction pulls on the hair follicle which elevates the hair = appearance of goose bumps)
What is the role of adipose cells?
Energy reservoir, thermal insulation pads and protects
How does skin act as a visual indicator of physiology and health?
- Characterises self image
- Reflects emotion
- Skin changes (colour indicates heat, emotion)
- Lesions or changes may reflect systemic infections / disease (i.e. jaundice = reduction in breakdown and excretion of bilirubin by liver)
What can skin be classified as?
- Thin
- Thick
Describe thin skin.
- Lacks stratum lucidum
- 4 layers
- Contains hair follicles, sebaceous glands and sweat glands
- Covers most of body
Describe thick skin.
- Found on palms of hands, soles of feet, corresponding surfaces of fingers and toes
- All 5 epidermal layers are contained
- Has sweat glands
- No hair follicles or sebaceous glands
Describe the outer primary layer.
- Barrier (tough, replaceable)
- Calluses can form (toughened and thickened skins; especially on feet and palms)
- Waterproof
What is the most abundant cell type in the epidermis?
Keratinocytes
Cells that contain keratin - but can be problematic as more keratin can cause cell death
What do melanocytes do?
Produce and store pigment melanin in response to UV exposure
What are Merkels discs?
Tactile receptors
What are Langerhans cells?
Epidermal dendritic cells which have an immune function and fight infection (have a phagocytic and protective function)
Describe the role of melanocytes.
- Have long, branching process which can contact other cells in higher layers to transfer melanin
- Melanin is produced in these cells and passed to cells around them
- Forms a protective barrier around the DNA of cells, preventing DNA damage due to UV light
Approximately how many melanocytes are there per mm^2
1000 - 2000 per mm^2
What are melanosomes?
Pigment granules
What is depth of skin colour determined by?
Primarily determined by the concentration of melanin in cells - NOT number of melanocytes
Which amino acid is melanin synthesised from?
Tyrosine
What is the dermis and how thick is it?
Connective tissue - contains collagen and elastic fibres, nerves, blood vessels, muscle fibres and hair follicles, adipose cells, glands
Describe the 2 sub layers of the dermis (corium).
- Papillary Layer: Loose areolar connective tissue, highly vascularised; friction ridges, Meissener’s corpuscles
- Reticular Layer: Dense, irregular connective tissue; ducts of holocrine, sebaceous (oil / sebum) glands and merocrine sudoriferous (sweat) glands; hair follicles; Pacinian corpuscles; Ruffini corpuscles
Describe the characteristics of Meissner corpuscles.
Looping axon terminals that intertwine supporting cells
Describe the characteristics of Merkel’s discs.
Dome structure atop axon terminals
Describe the characteristics of Pacinian corpuscles.
Sensory axon surrounded by fluid filled capsule (onion-shaped appearance)
Describe the characteristics of Ruffini endings.
Nerve terminals intertwined with collagen fibrils.
Describe the characteristics of Nociceptors.
Free nerve endings that penetrate epithelial cells, no morphological specialisation
What do cutaneous mechanoreceptors display?
Slow versus rapid adapting physiological response properties
What speed of adaptation and what receptive field size do Meissner’s corpuscles detect?
- Adaptation: Fast
- Receptive field size: Small
What speed of adaptation and what receptive field size do Pacinian corpuscles detect?
- Adaptation: Fast
- Receptive field size: Large
What speed of adaptation and what receptive field size do Merkel’s disks detect?
- Adaptation: Slow
- Receptive field size: Small
What speed of adaptation and what receptive field size do Ruffini’s endings detect?
- Adaptation: Slow
- Receptive field size: Large
Describe the hypodermis.
- Attaches skin to underlying organs, loose connective tissue and adipose tissue
- Also known as the subcutis or superficial fascia
- Extensive vascular network which promotes the rapid absorption of e.g. Drugs
- Normally thicker layers in women than in men, and regional distribution differs between genders
What is lanugo?
Hair grown in third trimester (fine, unpigmented), that is usually replaced by vellus
What is vellus?
Fine, unpigmented or lightly pigmented hair (primary human hair)
What is terminal hair?
Coarser, pigmented and longer hair on scalp, eyebrows and eyelashes
@ puberty, grows in auxiliary and pubic regions, and beard
Describe the cyclic growth of hair.
New hair grows in follicle internal to old one and pushes the old one out
Define ‘sebaceous gland’.
Sebum coats the hair to keep it supple
Define ‘hair papilla’.
Small amount of connective tissue, blood vessels and nerves
Define ‘hair matrix’.
Region of cell division
Cells divide and push upwards
Describe the medulla.
Central core is relatively soft, flexible keratin
Several layers form the harder ______ around the medulla.
Several layers form the harder cortex around the medulla.
Single layer of scaly cells forms the _______.
Single layer of scaly cells forms the cuticle.
What happens when body temperature rises above normal?
Nervous system signals dermal blood vessels to dilate and sweat glands to secrete = body heat is lost to the surroundings
What happens when body temperature drops below normal?
Nervous system signals dermal blood vessels to constrict and sweat glands remain inactive = body heat is conserved
Describe mechanical disruptions to the skin.
- Abrasions (horizontal disruption; painful (significant nervous fibre involvement))
- Lacerations (vertical disruption; less painful as fewer nerves involved))
What disruptions can affect the skin?
- Mechanical Disruptions
- Burns
- Cancer
Describe the different degrees of burns.
First Degree
- Red
- Sunburn
- Some pain
- Involves epidermis
Second Degree
- Blisters
- Very painful
- Involves all of epidermis and some of dermis
Third Degree
- Pain
- Nerve destruction
- Fluid loss
- Infection
- Black eschar scabs
- May extend into deeper tissues
Describe different types of skin cancers.
Basal Cell Carcinoma
- Stratum basale / germinativum
- Pearl like appearance
- Most common cancer
- Rarely metastasise
Squamous Cell Carcinoma
- Stratum spinosum
- Second most common cancer; elderly
- Can metastasise
Malignant Melanoma
- Melanocyte involvement / pre-existing mole
- Can metastasise, can be lethal
- ABCDE rule
What is the only contractile tissue in the body?
Muscle tissue
What can muscle tissue achieve?
- Excitability
- Conductivity
- Contractility
- Elasticity
- Extensibility
What does muscle contraction consume energy in the form of, and what does it generate?
Muscle contraction consumes energy in the form of ATP and generates heat.
What is muscle tissue rich in?
Rich in overlapping filaments known as myosin and actin (responsible for muscle shortening)
State the three types of muscle tissue.
- Skeletal Muscle
- Smooth Muscle
- Cardiac Muscle
Describe the characteristics of skeletal muscle.
- Voluntary movement
- Attach yo bones via tendons
- Striated in appearance
- Long cells with many nuclei
- Rapid and susceptible to fatigue
Describe the characteristics of smooth muscle.
- Involuntary movement
- Walls of blood vessels, gastrointestinal tract, uterus and parts of the urinary system
- Lacks striations
- Spindle-shaped cells with single nuclei
- Slower and indefatigable
Describe the characteristics of cardiac muscle.
- Involuntary movement
- Found in heart
- Striated in appearance
- Branched cells with single nuclei
- Intercalated discs electrically couple cells
- Rapid and indefatigable
What are the two main divisions of the nervous system?
- Central Nervous System
- Peripheral Nervous System
What is the Central Nervous System (CNS) divided into?
- Brain (Receives and processes sensory information, initiates responses, stores, memorises, generates thoughts and emotions)
- Spinal Cord (Conducts signals to and from the brain, controls reflex activities)
What is the Peripheral Nervous System (PNS) divided into?
- Sensory Nervous System (Detects stimuli and transmits information from receptors to the CNS)
- Motor Nervous System (Initiates and transmits information from the CNS to effectors)
What is the Sensory Nervous System of the PNS divided into?
- Somatic Nervous System (sensory input consciously perceived from receptors)
- Visceral Nervous System (sensory input is not consciously perceived from blood vessels and internal organs)
What is the Motor Nervous System of the PNS divided into?
- Autonomic Nervous System (motor output not consciously / is involuntarily controlled; effectors = cardiac muscle, smooth muscle and glands)
- Somatic Nervous System (motor output us consciously / voluntarily controlled; effector is skeletal muscle)
What is the Autonomic Nervous System divided further into?
- Sympathetic Division (fight or flight response)
- Parasympathetic Division (rest or digest response)
What is found at the superior end of the CNS?
Continuous with medulla at superior end
What is found at the inferior end of the CNS?
Becomes cauda equine at inferior end
What does the ‘brachial plexus’ refer to?
Nerves in the region of the arms
What does the ‘lumbar / sacral plexus’ refer to?
Nerves in the region of the abdomen, pelvis, legs
What are the two main components of nervous tissue? Describe the characteristics of each.
Neuronal Cells
- Excitable
- Cell body containing nucleus and organelles
- Elongated axon
- Transmits electrical information to effectors
- Axon terminals release neurotransmitter
- Myelinated or non-myelinated
- Elongated dendrites to receive information
Glial Cells (Neuroglia)
- Support
- Protective cells
Glial cells are up to how many times more numerous than neurons?
Glial cells are up to 10 times more numerous than neurons.
What are the major roles of glial cells?
Neuronal support cells
What are the main types of glial cells? Describe the characteristics of each.
Astrocytes
- Star shaped
- Most numerous glial cell type in brain
- Fill spaces between neurons
- Role: regulation of chemical environment
- Forms blood brain barrier
Oligodendrocytes & Schwann Cells
- Oligodendrocytes are present in CNS
- Schwann cells are present in PNS
- Wrap axon in spiral of fatty membrane
- Provide myelin (insulation for axons) and aid in impulse transmission
Microglia
- Small, phagocytic immune cells
- Derived from macrophages
- Functions: remove debris from dead/dying cells, repair
- Proliferate during inflammatory conditions
- Gliosis is the scar tissue formed as a result of microglial actions
Ependymal Cells
- Lining for ventricles
-
What are the 3 different types of neuronal cells, and what is distinct about each?
Unipolar
- Has an axon connected to a soma; no dendrites
Bipolar
- Has an axon connected to a soma, which is then connected to a dendrite
Multipolar
- Has an axon connected to a soma, which is then connected to several dendrites
Describe how an action potential passes across a neuromuscular junction.
1) Action potential travels down motor neurone
2) Causes release of neurotransmitter: acetylcholine
3) Acetylcholine binds to nicotinic receptors on muscle
4) Triggers depolarisation which can then spread across the muscle cell
5) Depolarisation triggers release of internal calcium stores
6) ATP and Ca2+ dependent mechanism causes skeletal muscle contraction
What is necessary for muscle contraction?
- Depolarisation
- Sufficient internal Ca2+
- ATP
