Mx2 Flashcards
What is cartilage and its function?
Cartilage is a resilient, avascular, connective tissue that consists of cells (chondrocytes) and a semisolid matrix
It provides support for some soft tissues in the body and forms a smooth sliding surface in moveable joints.
How are the types of cartilage distinguished?/
by the types of fibre embedded with the extracellular matrix of each type of cartilage
what constitutes the cartilage matrix that
gives the cartilage its resilience, firmness, flexibility and strength?
fibres, water and ground substance
What is the perichondrium?
the connective tissue that envelopes cartilage where it is not at a joint
Which type of cartilage forms most of the cartilaginous skeleton in the embryo and the fetus
hyaline cartilage
Where is hyaline cartilage present in childhood and adolescence?
epiphyseal growth plates, which are the sites of active bone growth - (its position can be seen in a long bone with unfused epiphysis and in radiographs of bone from a child)
Which areas can elastic cartilage be found?
external ear, Eustachian tube and epiglottis
Where is fibrocartilage found?
in areas of directional stress (e.g. intervertebral discs, pubic symphysis, articular discs associated with knee, in the temperomandibular and sternoclavicular joints) where resistance to compression, durability and tensile strength are needed
What happens when cartilage is damage or torn?
It is replaced by fibrous scar tissue laid down by fibroblasts. This may
prevent full restoration of cartilage function in the affected tissue.
Adult chondrocytes cannot undergo mitosis
What is periosteum?
a tough vascular fibrous connective tissue layer that surrounds bone
What is endosteum?
a thin cellular layer that lines the marrow cavity can be found internally in bone
What are the two forms in which bone exists?
Compact or dense (cortical)
Spongy (cancellous or medullary)
What do the central cavity of the long bones and spaces of the spongy bone contain?
bone marrow (red marrow, where active blood cell formation (haemopoiesis) occurs
and
yellow marrow which contains adipose (fat tissue) and where haemopoiesis does not occur
Where is compact bone found and what is its function?
Compact bone, which is found in shafts of long bones (e.g. femur) and flat bones (e.g. vault of the skull) provides primarily mechanical strength and protection of the underlying organs (e.g. brain in the case of the skull; heart and lungs in the case of the ribs and thoracic vertebrae
Where is spongy bone found and what is its function?
Spongy bone, which is found at the ends of long bones (e.g. humerus) and in the centre of flat bones and irregular bones (e.g. clavicle) provide space for the red marrow
what happens at the periosteum during the healing process?
proliferation of cell that form a soft cellular tissue mass that bridges the fracture site
Describe the healing process after a fracture
- Haematoma formation and local inflammatory response at the fracture site
- ingrowth of granulation tissue with formation of soft tissue callus
- formation of procallus composed of woven bone and cartilage with its characteristic fuisiform appearance and having 3 arbitrary components- external, intermediate and internal callus
- formation of osseous callus composed of lamellar bone following clearance of woven bone and cartilage
- remodelled bone ends; the external callus cleared away. intermediate callus converted into lamellar bone and internal callus developing bone marrow cavity
define neoplasia
A benign tumour of cartilage and bone are called a chondroma and osteoma respectively; malignant tumours are called chondrosarcoma and osteogenic sarcoma
What is Osteogenesis imperfecta?
a hereditary bone disease caused by a defect in collagen synthesis that results in the formation of an abnormal bone matrix; bones are thin and subject to multiple fractures (also known as ‘brittle bone disease’).
Give examples of surfaces of the ‘open’ cavities that are lined by moist mucous membranes
respiratory, digestive, reproductive and
urinary organs
State functions of skin
protection against microbial attack
prevention of fluid loss
temperature regulation
fine control of excretion, absorption
regeneration of skin tissues
sensation (fine touch and grip control)
Where do melanocytes reside?
at the junction between the epidermis and dermis (the basal layer –stratum basale).
How do melanocytes synthesis melanin?
Melanocytes synthesise melanin from tyrosine and package it into melanosomes that are transferred to the cytoplasm of keratinocytes
What is the main function of melanin?
The main function of melanin is to protect the skin against electromagnetic
radiation, primarily ultraviolet light, although it also affords a small amount of protection against radionuclides and X-rays too
What type of epithelium is found on the outer part of the lip and what lies beneath it?
stratified squamous
keratinised epithelium, beneath which lie the sweat glands, hair follicles and sebaceous glands, of normal facial skin
What type of epithelium covers the moist inside of the lip?
stratified squamous non-keratinised epithelium, with no hair follicles, sweat or sebaceous glands, but subtending salivary glands and much adipose tissue.
What is the vermilion zone?
The vermilion zone is an intermediate region between the normal facial skin and the moist inner region of the lip (i.e. the red external region of the lip, unique to humans).
What are the two types of hair on the human body?
Vellus hairs
Terminal hairs
Describe vellus hairs and where they are found
Vellus hairs, which are soft, fine, short and pale
Present on
most of the body’s surface (exceptions being the palms and sides of palms, soles and sides of the feet, dorsum of the distal phalanges of the fingers and toes, glans penis, glans clitoris, labia minora, and vestibular
side of labia majora).
Describe terminal hairs and where they are found
Terminal hairs are comparatively hard, large, coarse, long and dark, such as those found on the scalp and eyebrows. The density of hair follicles (number of hairs per cm2) in human skin is essentially the same as on other primates, but most human hair is vellus, whilst most other
primate hair is terminal
What is the function of hair on the head?
It provides UV protection, acts as cushion from trauma and as an insulator
What is the function of hair in the nostrils, ear canals and eyelashes?
hair prevents entry of
foreign material. It also has one final function as a sensory detector.
What do the Meissner corpuscles in the skin do?
detect heavy pressure and send sensations of ‘touch’ to the brain
What are the four primary mechanoreceptors in the human skin?
Merkel’s disks, which are unencapsulated, respond to light touch.
Meissner’s corpuscles, Ruffini endings, Pacinian corpuscles, and Krause end
bulbs are all encapsulated.
Meissner’s corpuscles respond to touch and low-frequency vibration.
Ruffini endings detect stretch, deformation within joints, and warmth.
Pacinian corpuscles detect transient pressure and high-frequency vibration.
Krause end bulbs detect cold.
What is the function of a fingernail and toenail?
of protecting the distal
phalanx (fingertip or tip of the toe), and the surrounding soft tissues from injuries
How does the nail enhance precise delicate movements of the distal digits?
through counter-pressure exerted on the pulp of the digit. The nail then acts as a counter-force (lever) when the end of the digit touches an
object, thereby enhancing digit sensitivity even though the nail itself has no
nerve endings.
what is the tool-like function of the fingernail?
extended precision grip- helps for pulling out a splinter
What happens to the epidermal layer as a nail grows out from the nail root?
The epidermal layer
of epithelial cells proliferate
squamous epithelial cells furthest form the cuticle (lunula) die during this process and produce a layer of
flexible but strong compact cells that interdigitate with the keratin protein layers.
What form of gland is the sebaceous gland
branched form of acinar gland
What is a pilosebaceous unit?
A structure
consisting of hair, hair follicle, arrector pili muscle, and sebaceous gland
Which non-haired areas are sebaceous glands found?
eyelids, nose, penis, labia minora, and
nipples
What is the name of the specialised form of sebaceous gland found at the rim of the eyelids and what does it secrete?
meibomian (tarsal) glands secrete a form of sebum (known as meibum) onto
the eye, which slows the drying of tears form the cornea
How does sebum and keratin cause pimples?
In the skin pores, sebum and keratin can create a
hyperkeratotic plug called a “microcomedo”, which can block a pore and cause pimples
What are sweat glands?
small tubular structures of the skin that produce sweat
exocrine gland
What are the two types of sweat glands?
Eccrine sweat glands
Apocrine sweat glands
Where are eccrine sweat glands distributed?
almost all over the human body,
in varying densities, with the highest density in palms and soles, then on the head, but much less on the trunk and the extremities
Where are apocrine sweat glands found?
mostly limited to the axilla (armpit) and
perianal areas in humans
What is the difference between sweat excreted by eccrine and apocrine sweat glands?
Eccrine: water-based secretion represents a primary form of cooling in humans.
Apocrine: secrete continuously secrete their oily, odorless sweat fluid (with proteins,
lipids, and steroids) in periodic spurts
What are the three distinct layers of the skin?
Epidermis
Dermis
Hypodermis
Describe the epidermis
superficial, epithelial, avascular layer
Describe the dermis
deeper and provides support for the epidermis. The
dermis contains connective tissue elements, parts of the skin appendages (i.e.
hair follicles and nail beds) and vascular and nervous structures. The dermis rests on top of the lowest layer
Describe the hypodermis
a layer of loose connective tissue with adipose tissue (fat) cells, sweat and sebaceous glands, and larger blood vessels
what is psoriasis?
Psoriasis is an autoimmune skin condition that causes red, flaky, crusty patches of skin
covered with silver-coloured scales.
Psoriasis occurs when skin cells are replaced more quickly than usual
Where do psoriasis patches normally appear?
elbows, knees, scalp and lower back, but can appear anywhere on the body
What is the result of skin cells on people with psoriasis only taking 3-7 days to reach the epidermis?
cells that have not yet fully matured accumulate and the outer layer of keratin, which is relatively thin is lost causing the signs of crusty red patches covered with silvery scales. The cells at the surface are also lost very quickly too as they are ‘rubbed’ off
What is ezcema?
Eczema, also known as atopic dermatitis, is a chronic skin condition that makes the skin red, dry, itchy, and cracked
It can occur at any age
How is ezcema caused?
skin inflammation
How does ezcema impact quality of lie and create a psychosocial burden?
Eczema can also have psychological and social impacts:
Children with allergic eczema have a worse quality of life than children
with asthma, diabetes, or epilepsy
Children with allergic eczema may also miss days of school, skip activities,
and feel social isolation
What are the symptoms of ezcema?
The main symptoms are:
A dry, itch skin and rash
In more severe cases, the skin might show signs of:
Inflammation, cracking and bleeding and can be extremely painful.
