PBL Week 6 Flashcards
What are the different anatomical terms?
Body split into 5 regions: head, neck, upper limb (arm, forearm, wrist, hand), lower limb (thigh, leg, ankle, foot) and the trunk (thorax, abdomen, pelvis).
The nearer somewhere is to the point of reference/attachment (e.g shoulder) the more proximal it is. The further away, the more distal it is.
4 planes through the body: saigttal (vertically through middle of body when forward facing), parasagittal (vertically through shoulder and leg when forward facing), coronal (vertically through middle of body when side facing) and transverse (horizontally sideways through waist).
Superior/cranial - closer to the head
Inferior/caudal - closer to feet
Medial - (closer to sagittal plane)
Lateral - (further from sagittal plane)
Posterial//Dorsal - (closer to back when body is side-on)
Anterior/Ventral - (closer to chest when body is side-on)
Flexion - extending muscle inwards
Extension - extending muscle outwards
Abduction - moving a body part away from midline
Adduction - moving a body part towards the midline
External rotation - rotation of limb away from the body
Internal rotation - rotation of limb inwards to the body
Pronation - extremeties facing upwards
Supination - extremeties facing downwards
What are the layers of the body?
Top layer - skin. Acts as a barrier and as a sensory organ. Made of epidermis, dermis and subcutaneous tissue.
Fascia - layers of connective tissue (collagen) that surrounds organs and muscles. Provides support and compartmentalises groups of structures together. Can be superficial, deep or visceral fascia depending on location.
Muscles - bring about movement by shortening the difference between 2 fixed points and by expending energy. Controlled by nerves and joined to bone by tendons.
Bone - internal scaffolding of body. Cannot move on it’s own - needs muscles. Ligaments attach bones to other bones. Where 2 bones meet, it’s called a joint.
How do muscles help us move?
3 types - skeletal, smooth and cardiac muscle. Skeletal muscle is used in movement. Each muscle is a bundle of fibres, wiith each fibre being a giant, multinucleated cell. These fibres contain overlapping bundles of myofibrils (thick myosin filaments and thin actin filaments). These are arranged in units called sarcomeres.
One the outside of the myosin are “heads”, which are in a flaccid position at rest. One a signal reaches the muscle, an ATP connects to the head and is hydrolysed, allowing the head to stand up in a high-energy configuration. The head binds to the actin above it, forming a cross bridge. The head then loses it’s ADP and returns to the flaccid position, dragging the actin along as it does, essentially shortening the sarcomenre and contracting the muscle. The head then detaches, ready to start again.
The muscle all contract at once due to T-tubules running through the fibre, allowing the nervous signal to hit every myofibril at once. The fibre is also covered in the sarcoplasmic reticulum (SR), which releases calcium ions when the nervous signal reaches it. This calcium allows the myosin heads to bind to the actin.
What are the types of bone and the different roles for bones?
There are 2 types of bone - the hard, strong, compact and dense cortisol on the outside (80%) and the honeycomb, spongey cancellous on the inside (20%). Calcium is what gives bones their hard structure - around 98% of the body’s calcium is stored in the bones. This is regulated by vitamin D, parathyroid hormone (PTH) and calcitonin.
The bones also store phosphate ions as well; around 85% of our phosphate is stored in the bones.
Bones also offer support, giving us a defined shape. They also allow us to transmit the force of muscle contractions and let us move. They also protect our organs.
Red blood cells, white blood cells and platelets are made in our bone marrow, a process known as hematopoiesis.
How does bone structure and function change throughout our life?
At 12-16 weeks, the skull and mandible is more calcified while the other lay down a cartilage model that eventually ossifies. This comes in 2 types; intramembraneous (cranial and facial) and endochondral (axial skeleton and limbs). Endochondral ossification happens as follows:
Hyaline cartilage model is laid down by chondrocytes, these become trapped inside the model as it ossifies (primary ossification centre). Then, osteoblasts produce and lay down further material that ossfies (starts at middle of the bone and spreads to extremities). There are also secondary ossification centers on the end of bones, which ossify and meets the ossification from the shaft.
Bone development controlled by bone morphogenic proteins (BMPs), which induce stem cell differentiation into bones. Hedgehog proteins (HH) also important for bone formation, in particular sonic and inidan HHs.
Osteons are continually-replaced rings which make up bone, which is also lined with osteocytes. Osteoblasts, used in bone formation, make up an osteoid collagen matrix and regulated mineralization to create osteons or osteocytes.
Osteoclasts are large cells used to break fown bone. They form from Howship’s Lacunae, which use H+ ions to break down the mineral part of the bone and lysozymes/proteases to break down the bone matrix.
What are the different hormones that affect bone growth?
Parathyroid hormone (PTH) maintains the calcium levels and stimulated formation of bone, calcitriol stimulates intestinal calcium absorption and calcitonin, which inhibits bone breakdown. The pituitary gland secrets growth hormone (GH), which increases calcium retention and bone length. The thyroid gland produces thyroxine, which promotes osteoblast activity. Finally, both oestrogen and testosterone are important in maintaining bone health. At the menopause, however, the levels of oestrogen in females fall dramatically, leading to an increased risk of osteoporosis due to the decreased bone density. This is also a risk for men as they age, but not as much.
How can the differences in genes and the environment impact our bone health?
Certain genes can increase the risk for various bone diseases. For example, the DARC gene makes a protein that helps break down bones more than in people without the gene, lowering bone mineral density and increasing the risk of developing osteoperosis.
Rickets/osteomalacia are caused by a lack of vitamin D or Calcium. People who don’t get a lot of direct sunlight or who don’t have a lot of calcium in their diets are at risk of developing it. They can also be caused by genetic defects, too.
Describe the neurobiology of bone.
Bones are innervated by both myelinated and unmyelinated sensory neurons. They are used as regulators for mechanical forces and as a source of trophic factors essential for bone structure and function.
What are the investigations involved in diagnosing bone diseases?
Lab tests on body samples - for example, lower levels of oestrogen in the blood could indicate osteoporosis.
X-rays - are able to show general injuries such as fractures or arthritis.
MRI - shows soft tissue such as any issues with the bone marrow cavity or bone tumours.
Bone densitometry - measures bone mass in spine, hips and arms, used to diagnose osteoporosis.
Radionuclide bone scan - used to pinpoint location of brain tumours or to diagnose stress fractures/other tiny cracks.
What is the historical basis for dissection and what are the ethical protocols in place today?
Were incredibly important in the past in investigating the human anatomy and how they worked. Whether they should be used for teaching nowadays is debated, however.
One one hand, we now have the tech to learn anatomy in less invasive ways. Furthermore, cadavers are costly to obtain and aren’t representative of a live person. However, some argue that it makes learning easier and shows the anatomical differences between people. There are also many less autopsies carried out in hospitals due to advances in diagnosing diseases.
If dissections do take place, the body must be given respect, dignity and anonymity. General lab rules apply in a dissection lab. The face of the donor is to be hidden at all times.
What are the bone diseases previously linked to poverty and what are their current prevalence?
Rickets/osteomalacia - due to lack of vitamin D or calcium, affected the poor in victorian england, but disappeared over 80 years ago due to discovery of cause. Is now making a comeback due to sedentary lifestyles and poor diets resulting in a lack of vitamin D and calcium. Is more common in Africa, as darker skin absorbs less vitamin D, and in Asia, where pollution causes lack of sunlight.
Osteoporosis also linked to poor diet and povery, meaning that they have a high prevalence in those who are have lower incomes.
