Chapter 1 Flashcards
The body is composed of four basic tissues:
Epithelial
Connective Tissue
Muscle
Nerve
What tissues compose the skin?
Epithelial and Connective Tissue
What cells compose the epidermis?
Stratified squamous keratinised epithelium
What are the various skin appendages?
Sweat glands
Sebaceous glands
Nail
Hair
Name the embryological origin of the epidermis
Ectoderm
Name the embryological origin of the dermis
Mesoderm
What is the main tissue component of the dermis?
Connective Tissue
Name the upper most layer of the epidermis
Stratum corneum
What is the composition of the stratum corneum?
Cornified layer of dead keratin cells which have lost their nuclei and are constantly being replaced by deeper layers
What causes variation in thick and think skin?
Depth of the stratum corneum
thick - sole of feet; thin - forearm
Where are melanocytes situated?
Basal layer of the epidermis
How do melanocytes influence skin colour
Generate melanin
Liberated from cell
Ingested by epidermal cells
How can synthesising melanocytes be distinguished from a epidermal cell that has ingested melanin?
DihydrOxyPhenylAlanine (DOPA) - tryosinase enzyme is converted to melanin
What property of melanocytes influences the skin colour of an individual
Activity
high - dark, low - pale
What are skin creases?
Flexure lines over joints where the skin is thinner and bound firmly to underlying structures e.g. deep fascia
What regions do not contain sweat glands?
Lips, glans penis, tympanic membranes
In which region are the greatest concentration of sweat glands?
Palms and soles
Face - forehead
Describe the structure of sweat glands
Coiled test-tube that extend below the dermis as straight ducts and corkscrew through the epidermis
Describe the two types of sweat glands
Eccrine - majority, transport H20 to the bdoy surface for thermal regulation
Apocrine - larger, equivalent of scent glands, confined to the axillae, areola and urogential regions. Controlled by sex hormones.
Where do the ducts of apocrine glands terminate?
Open at a hair follicle
Where are sebaceous glands found?
Hairy skin - short duct at side of hair follicle
Directly on skin surface - eyelids, lips, papillae of breasts and labia minora
Describe the hair matrix
region of epidermal cells at the base of a hair follicle through which cells transcend inside the tubular epidermal sheath, lose their nuclei and are converted into hard keratin rods
What causes different hair colour?
The mixture of three different pigments imparted by melanocytes
Why does hair colour change with age?
Decreased melanocyte activity
What causes hair to “stand on end”
Arrector pili muscle - smooth muscle, autonomic innervation
Describe the “Rule of 9’s”
Used to estimate affected surface area in burns
Head and Upper limb - 9% each
Lower limb, front of thorax and abdo, back of thorax and abdo - 18%
Why are tension lines of skin important?
Incisions made along creases and wrinkles heal with minimal scaring
What connects the skin to the underlying bones/deep fascia?
Areolar tissue
What is the fat layer of areola tissue called?
Panniculus adiposus
Describe the panniculus carnosus
Flat sheets of muscle in the panniculus adiposus
What are the attachments of the panniculus carnosus?
skin - muscle fibre - deep fascia/bone
Well-developed panniculus carnosus form which muscles?
Platysma Palmaris brevis Unstriped muscle of the corrugator cutis ani Dartos sheet of the scrotum Subareolar muscle of the nipple
Define deep fascia
Membrane of fibrous tissue that encloses the body wall and limbs
Give an example where the deep fascia is:
i) prominent
ii) almost absent
iii) absent
i) Iliotibial tract of the fascia lata
ii) Rectus sheath of the external oblique aponeurosis
iii) Face and Ischioanal fossa
While deep fascia passes freely over bone it remains anchored to what structure?
Periosteum
Deep fascia is very sensitive - what is its nerve supply?
Same nerve innervation as the overlying skin
What is the composition of a ligament?
Dense connective tissue - predominantly collagen fibres
What are the attachments of a ligament?
Bone to bone
Describe the physical properties of ligaments
Non-elastic/Unstretchable
If subject to prolonged strain collagen fibres will elongate and undue mobility is possible
White fibrous tissue ligaments are never subjected to prolonged strain - name the two exceptions
Sacroiliac ligament
Intervertebral discs
subject to strain of whole body wt, except when recumbent
Name to ligaments composed of yellow elastic tissue
Ligamentum flava
Capsular ligaments of the joints of the auditory ossicles
What are the attachments of a tendon?
Muscle to bone
Describe the structure of a tendon
Similar to a collagenous ligament - may be flat/cylindrical
Where do tendons derive their blood supply?
From vessels descending the muscle body
They anastamose to the periosteum of the bony attachment
What is the purpose of a synovial sheath?
To lubricate tendons that bear weight on adjacent structures
Describe the structure of a synovial sheath
Parietal layer - attached to the surrounding structures
Visceral layer - firmly fixed to the tendon
Synovial fluid - lubricating thin film of luid
Define “raphe”
Interdigitation of the short tendonious fibres of flat muscle sheets.
Raphes can be elongated passively by separation of either attachment
Give an example of a raphe
Pterygomanidbular raphe
Buccinator and superior constrictor interdigitate to vary the position of the mandible
Define “cartilage”
Dense connective tissue in which cells and fibres are embedded in a matrix
Describe the 3 types of cartilage
Hyaline - covers articular surfaces of synovial joints; forms epiphyseal growth plates
Fibrocartilage - intervertebral discs; disc like structure i.e. labrum of the shoulder and hip/menisci of knee; articular surface of clavicle and mandible
Elastic - pinna, epiglottis
How is cartilage repaired?
Formation of fibrous tissue - avascular
Capable of a small amount of deformation - resistant to fracture.
Describe the appearance of fibrocartilage
Similar to ligaments and tendons
Contains small islands of cartilage cells with ground substance embedded between the cartilage bundles
Describe what happens to hyaline and fibrocartilage with ageing?
Calcification and Ossification
Describe the structure of elastic cartilage
Ground substance containing large number of elastic fibres
How does cartilage receive blood?
Fibrocartilage - ordinary blood supply which is sparse, therefore low metabolic rate
Elastic/Hyaline - have no capillaries, exchange occurs through diffusion of the ground substance
Name the 3 kinds of muscle
Skeletal - multinucleated
Cardiovascular - single nucleus
Smooth - single nucleus
What are the 2 histological classifications of muscle
Striated
Non-striated
Which muscles are striated?
Skeletal and cardiac muscle
What causes striation?
Arrangement of mysoin and actin fibres
Describe the appearance of smooth muscle
Narrow spindle shaped cells
Parallel in muscles of peristalsis
Whorls/Spirals for mass contraction i.e. bladder/uterus
How is smooth muscle innervated?
Autonomic nerves - contractile impulses transmitted through gap junctions
Describe the appearance of cardiac muscle?
Broad, short cell branches
Adjacent cells interdigitate at their intercalated discs to increase surface area for conduction
Arranged in whorls/spirals to support cardiac ejection
How is cardiac muscle innervated?
Autonomic nerves
Describe the appearance of skeletal muscle
Non-branching fibres bound by loose areolar tissue containing fibroblasts and macrophages
What is the epimysium?
Membranous envelope of connective tissue that encapsulates the muscle
Varying thickness and density
Describe the 2 muscle fibres composing skeletal muscle
Red fibres - slow twitch, aerobic respiration, high mitochondrial content, myoglobin, succinate dehydrogenase and low myosin ATPase
White fibres - fast twitch, anaerobic, high glycogen and phosphorylase content
True or False: the fibres of a single motor unit are all the samei.e. white or red
True - unless the nerve supply is altered i.e. regeneration after injury
What is a muscle spindle?
Intrafusual fibre - specialised muscle fibre encased in a connective tissue capsule
Constant in position and most numerous in muscles concerned with fine movement
What is the innervation of intrafusal fibres?
Gamma motor neurons of the anterior horn
What is the innervation of extrafusal fibres?
Large alpha cells
Describe the function of muscle spindles
Sensory receptor - informs the CNS of a muscles state of contraction
How does individual muscle disposition influence activity?
Parallel - maximal range of mobility
Oblique - increased force of pull
What are the 3 patterns of oblique muscle disposition?
Unipennate muscles - tendon forms along one margin e.g. flexor pollicis longus
Bipennate muscles - tendon forms centrally (usually as a fibrous septum)
e.g. rectus femoris
Multipennate muscles - series of bipennate muscles lying side-by-side
e.g. acromial fibres of deltoid, subscapularis
cylindrical muscle in which a central tendon forms
e.g. tibialis anterior
What does a smooth mark on a bone indicate
Tendon or ligament attachment
Rough marks - mixture of flesh/tendon or lengthy aponeurosis
Define “movement”
Co-ordinated activity of many muscles usually assisted by gravity
Define “prime-mover”
Desired movement e.g. biceps flexing elbow
What is an antagonist?
Opposite of desired movement
e.g. triceps relax to assist elbow flexion
Define “fixator”
Stabilisers one attachment of a muscle so that the other end may move
E.g. muscles holding the scapula in place as the deltoid moves the humerus
Define “synergist”
Prevent unwanted movement
E.g. stabilisation of flexor and extensor carpi ulnaris as finger flexion occurs
What is the innervation of skeletal muscle?
Somatic nerves via one or more branches, which also contain afferent and autonomic fibres
What are the efferent fibres in spinal nerves?
Axons of the large alpha anterior horn of the spinal cord.
Pass to extrafusal fibres and small gamma cells which supply the spindle (intrafusal fibre)
How are the skeletal muscles of cranial nerves supplied?
Motor nuclei of cranial nerve
What is a limb plexus?
Branch of nerves supplying a limb muscle.
Flexor muscles - anterior division of nerve plexus
Extensor muscles - posterior division of nerve plexus
A nerve to the body wall or in a limb contains approx what % of afferent fibres?
40% - these innervate muscles spindles and mediate proprioceptive impulses - vital for co-ordinated muscle contraction
Which nerves supply the ocular and facial muscles?
Cranial Nerves III, IV, VI and VII - contain no afferent fibres
How are proprioceptive impulse conveyed form the ocular and facial muscles?
Via local branches of the trigeminal nerve
Which crainal nerves contain no afferent fibres?
Cranial nerves III, IV, VI, VIII, XI, XII
Proprioceptive impulses are conveyed for/via
Hypoglossal nerve via C2/C3 SCM
Accessory nerve via C3/C4 trapezius
Describe the composition of bone
Dense connective tissue with cells and fibres embedded in a calcified ground substance, termed bone matrix
What are Harvesian canals?
Large space within bone containing blood capillaries which communicate with cannaliculi
What are lamallae?
Concentric layers of matrix laid down in bone development
What are Volkmanns canals?
Anastamosing vessels between Haversian canals
Describe the 2 macroscopic forms of bone
Compact bone - hard and dense
Cancellous bone - spongy trabeculae arranged to resist stress and strain
How does bone remodelling occur?
Influenced by stress
Resorption occurs by phagocytic osteoclasts
Deposition of new bone occurs by osteoblasts
What is the name of the deeper layer of the periosteum and what does it do?
Osteogenic layer - contains cells that differentiate into osteoblasts
What are Sharpey’s fibres?
Attach the periosteum to underlying bone - particularly strong at sites of tendon/ligament attachment
Does periosteum cover the articularting surface of bones in synovial joints?
No
How many layers comprise the endosteum?
1
What is fracture callus?
Mass of inflammatory tissue and bone forming cells present at a fracture site
What is indicated by excessive cartilage formation?
Mobilised fracture site
Define “osteochondrogenic”
Well vascualrised areas are osteogenic and produce new bone
In areas that become avascular chondrogenic cells form hyaline cartilage instead
What are the 2 main processes of bone development?
Intramembranous ossification - vault of the skull, face and clavicle
Enbdochondrial ossification - long bones of the skeleton
What is sub-periosteal ossification?
Development of bone thickness - occurs by intramembranous ossification
Describe intramembranous ossification
Destruction of pre-exisitng hyaline cartilage
Replaced with bone
What is the primary center of ossification in long bones?
Site where bone firsts form
E.g. diaphysis in long bones
Describe secondary cartilage
Provision of cartilage surface on membrane bones
i.e. head of the mandible, ends of the clavicle
How does the appearance of secondary cartilage vary from hyaline cartilage?
Secondary cartilage - larger cells, closely packed, more fibrous matrix
What is a sesamoid bone?
Seed like bone usually associated with tendons that glide over adjacent bone
i.e. patella
Give 3 examples of sesamoid bones
Patella
Flexor pollics brevis sesamoid bone
Peroneus longus tendon - prevents friction of cuboid bone
Give the 3 possible unions between bones
Fibrous joint
Cartilaginous joint
Synovial joint
Describe a fibrous joint
Between bones or cartilage, formed by fibrous tissue
Negligible movement
e.g. bones of the vault of the skull, lower end of the tibia and fibula
Describea primary cartilaginous joint
Union of bone and hyaline cartilage
Immobile and very strong
e.g. Epiphyses, ribs and costal cartilage
Describe a secondary cartilaginous joint (symphysis)
Union between bones with a thin lamina of hyaline cartilage united by fibrocartilage
Limited movement
Cavity in fibrocartilage - never lined with synovium
e.g. pubic symphysis, sternomanubrial joint, intervertebral disc (gel filled)
Detail the 6 features that characterise synovial joints
Ends covered in hyaline cartilage
Surrounded by a capsule which encloses a…
Joint cavity = capsular ligament
Ligaments - internally/externally reinforce the joint capsule
Synovial membrane - lines the internal joint capsule
Movement
Define “closed-pack” in terms of a joint
Surface of two bones in maximal contact with reinforcing ligaments under greatest tension
Where are intra-articular fibrocartilages found?
Occur in joints where 2 separate movements take place
Sternoclavicular joint - elevation and depressino
Knee - rotation
What is the circulus vasculosus (Fig 1.9)
Vascular plexus between the capsule and synovial membrane.
Attached to the epiphyseal line
Branches supply the synovial membrane and joint mesenchyme
Anatomically - why was the metaphysis a common site of osteomyelitis in children?
Blood vessels cannot communicate across the cartilaginous epiphysis
Arteries arising from the shaft form end arteries at the metaphysis - prone to embolism/infarction
Once the epiphyseal plate ossifies, vascular communication is established
Why is joint pain poorly localised?
Joint capsules and ligaments contain some myelinated nerve fibres
Synovial membranes have few
Articular cartilage has no afferent fibres
List 3 components of joint stability
Bony contour
Ligaments
Muscle
What happens to white fibrous tissue (collagen) and yellow elastic tissue under continuous stretch?
White fibrous tissue - elongates
Yellow elastic tissue - shortens after elongation to maintain stability
How are the arches of the foot stabilised?
Muscles
Ligaments contribute little stability as they are continuously stretched
Define “mucous membrane”
Lining of an internal body that communicates with exterior
What layers compose a mucous membrane?
Epithelium
Lamina propria - underlying connective tissue
Muscularis mucosae - smooth muscle
Define “serous membrane”
Lining of a closed body cavity e.g. pericardial, pleural, peritoneal
Layer of connective tissue and single flattened mesothelial cells
What are the two layers of a serous membrane?
Parietal layer - loosely attached to areolar tissue
Visceral layer - adheres tightly to viscera
What is the innervation of the parietal layer of a serous membrane?
Somatopleure - supplied segmentally by spinal nerves
What is the innervation of the visceral layer of a serous membrane?
Spalnchopleuere - no sensory supply
Why are there more veins then arteries?
Hydrodynamics - veins are larger but operate under less pressure
What is the purpose of dead space around a vein?
Accommodates dilatation secondary to increased blood flow
Name the 3 layers of blood vessel and describe how they vary in different vessels
Tunica intima - one layer in capillaries; contains the internal elastic lamina in arteries
Tunica media
Tunica adventitia
What layer is missing from the wall of the inferior vena cava?
Tunica media
Which veins do not contain true valves?
Superior and Inferior vena cava
Veins of the head and neck, vertebral, cardiac, pulmonary, hepatic and pelvic veins
Describe the 2 types of arterial anastamoses
Actual - arteries meet end to end; cut vessel will spurt from both ends
E.g. labial branches of the facial arteries, intercostal arteries, uterine and ovarine, greater/lesser curvature of stomach, arterial archades of the mesentry, marginal artery of the colon
Potential - anastamosis is by terminal arterioles - given sufficient time arteries will dilate to take blood.
Sudden occlusion may yield inadequate nourishment
E.g. coronary arteries, limb arteries anastamose in the region of the joint, cortical arteries of the cerebral hemisphere
What lymphatic vessels typically accompany veins and arteries?
Superficial lymphatics - veins
Deep lymphatics - arteries
Describe the 2 types of immune response
Humoral antibody response - production of antibodies (protein molecules) which circulate in the blood, attach to foreign proteins forming an antigen-antibody complex, removed by phagocytosis
Cell mediated immune response - production of specific cells that circulate in the blood and target antigens for destruction/phagocytosis
Detail the 2 types of lymphocytes
T cells - cell mediated immunity
B cells - humoral antibody production, transform into plasma cells which give rise to immunoglobulins
Where do T cells reside?
Spleen, lymph nodes and lymphoid follicles
What are the sites of origin and development of immune cells?
Stem Cells
T cells - thymus
B cells - bone marrow
Name the lymphoid glands
Thymus
Lymph nodes
Spleen
Tonsils
What are Peyer’s patches?
Collection of lymphoid follicles in the ileum
What is GALT?
Gut associated lymphoid tissue - largest mass of lymphoid tissue in the body
What are M cells?
Overlying mucosal lymphoid follicles at enterocytes
Absorb antigenic material - expose it to intrapeithelial and follicular lymphocytes/macrophages to stimulate an immune response
Describe the structure of the thymus
Dense band of lymphoid tissue at the cortex of the lobules.
Inner pale medulla containing the corpuscle of Hassall - remnants of epithelium of the 3rd pharyngeal pouch
Within a lymph node where are B and T cells found?
B lymphocytes - follicles and medulla
T lymphocytes - paracortical areas (thymus dependent zone) and in the cortex between follicles
Which two lymph organs have no afferent vessels?
Spleen and Thymus
What distinguishes lymph nodes from tonsils?
Tonsillar crypts - stratified squamous epithelium
What is the reticuloendothelial sytem?
Monocyte/macrocyte system which facilitates phagocytosis
Detail the 2 divisions of the nervous system
Central Nervous System - Brain and Spinal Cord
Peripheral Nervous System - Cranial Nerves, Spinal Nerves and associated ganglia
Describe the somatic and autonomic parts of the nervous system
Somatic - innervation of skeletal muscle and transmission of sensory information
Autonomic - control of cardiac and smooth muscle, glands
Define a “neuron” and its components
Structural and functional unit of the nervous system
Nucleus (cell body) with multiple nerve fibres
Single cytoplasmic process - axon, conducts nerve impulses away from the cell body
Multiple cytoplasmic processes - dendrites, reception of stimuli
Define “diffuse neuroendocrine system”
Multiple synapses with receptors for neurotransmitters and endocrine function.
Noradrenaline, acetylcholine, neuroendocrine cells/neuromediators/amine precursor uptake and decarboxylation (APUD) cells
Cell bodies with similiar functions show tendency to group themselves together and form ____ within the CNS and ____ outside it.
Similarly, processes from such aggreations of cell bodies tend to run in bundles forming ____ within the CNS and ___ outside the brain and spinal cord
Nucei Ganglia
Tracts Nerves
Name the different types of neuroglial cells
Astrocytes - derived from ectoderm
Oligodendrocytes - derived from ectoderm
Microglial cell - phagocytic cell corresponding to a macrophage of connective tissue, derived from mesoderm
Satellite cells (ganglia) - ectoderm
Schwann cells (peripheral nerves)- ectoderm
Name the 2 myelin forming cells
Oligodendrocytes - CNS
Schwann cells - PNS
What are the Nodes of Ranvier
Site of adjacent myelinating cells
Describe the varying sizes of peripheral nerve fibres and associated function
Group A - up to 20um in diameter:
alpha - 12-20um. Motor and proprioception (Ia and Ib)
beta - 5-12um. Touch, pressure and proprioception (II)
gamma - 5-12um. Fusimotor to muscle spindles (II)
delta - 1-15um. Touch, pain and temperature (III)
Group B - up to 3um diameter. Myelinated
- preganglionic autonomic
Group C - up to 2um diameter. Unmyelinated.
- post ganglionic autonomic, and touch and pain (IV)
How many pairs of spinal nerves are there in the human body?
31.
8 - cervical 12 - thoracic 5 - lumbar 5 - sacral 1 - coccygeal
Cervical/Sacral/Lumbar/Brachial nerve plexii form from which rami
Anterior rami
What are nervi nervorum?
Nerves lining the connective tissue covering a larger nerve.
What are the properties of:
- mixed nerves
- cutaneous nerves
mixed nerve - motor, sensory, proprioception
cutaneous nerves - touch/pain/temperature
Describe the innervation of the body wall
Innervation occurs segmentally by the spinal nerves
Posterior rami - extensor muscles of vertebral column, skull and overlying skin
Anterior rami - all other muscles of the trunk and limbs, overlying skin.
