Summary Human Anatomy key points.

Anatomy and physiology



Anatomical nomenclature

 Refers to anatomical positions standard reference for describing the body

 Arms at the side palms facing forwards, feet shoulder width apart, toes forward
(this is the position you assume the body, regardless of actual orientation).

 Prone- face down

 Supine- face up

 Brachium = upper arm

 Antebrachium = forearm

 Femur = thigh

 Crus = leg (knee- ankle)

 Anterior/ventral , front, toes are anterior to the foot (toes are Infront of the foot)

 Posterior/ dorsal, back, popliteus is posterior to patella (popliteus is behind the
patella)

 Superior/ cranial, above, orbits are superior to the oris

 Inferior/ caudal, below, pelvis is inferior to abdomen.

 Lateral, towards the side, thumb is lateral to digits

 Medial, towards midline, hallux is the medial toe (middle toe)

 Proximal, near trunk, brachium proximal to antebrachium

 Distal, away from trunk, crus distal to femur

 Superficial, near surface, skin is superficial to bones

 Deep, far from the surface, the brain is deep to the skull.

 Sagittal plane- divides body into left & right. (midsagittal= equal halves.
Parasagittal= unequal halves).

 Frontal (coronal) plane= divides body into anterior and posterior

 Transverse (horizontal) plane = divides body in superior and inferior, produces
cross sections.

 Dorsal (posterior) cavity = cranial cavity (brain), vertebral cavity (spinal cord).

 Ventral (Anterior) cavity= thoracic cavity (lungs, heart (in mediastinum).
Abdominopelvic cavity- abdominal (digestive organs), pelvic (reproductive organs).

Abdominal regions & quadrants

Nine regions

 Right/left hypochondriac

 Right/ left lumbar

 Right/left iliac

 Epigastric

 Umbilical

,  Hypogastric

Four quadrants

 Right upper (RUQ)

 Left upper (LUQ)

 Right lower (RLQ)

 Left lower (LLQ)



Genes

 A gene is a segment of DNA that give cells instruction for a specific trait or body
function.

 Genes code for proteins which control everything from appearance to internal
functions

 Human have 20000 genes that code for proteins

 Genes are packaged in chromosomes inside the nucleus

Genes and alleles

 You inherit two copies of each gene- one from each biological parent.

 Alleles= different versions of the same gene

 Genotype= alleles you carry

 Phenotypes= traits your show

How genes work

 DNA - mRNA (transcription) mRNA copies the genes instructions.

 mRNA - Protein (translation) Ribosomes read mRNA in codons (3 letter sequences)
each codon= specific amino acid or start/stop sequence.

 There are 20 amino acids, but >100,000 proteins in humans.

 Genes can be turned on/off depending on cell type, injury, illness, or environment
(epigenetics)



Cell differentiation

 Cell differentiation is the process in which unspecialised cells become specialised in
structure and function

 Formation of tissues, organs and body systems

 Replacement of damaged or dead cells

 Cancer

 Developmental disorders.



Pattern formation

 Is the process in which cells in a developing embryo acquire spatial organisation,
forming tissues, organs and body axes.

 Morphogens= signalling molecules distributed in gradients

,  Sonic hedgehog (Shh) gradient in limb development ( high Shh- posterior digits
(little finger), low Shh- anterior digits (thumb)).

 Positional information= cues that tell a cell where it is

 Segmentation= repeated structural units

 Collinearity- Hox gene order matches body axis order.

Ontogeny

 Refers to the entire developmental journey of an organism from fertilisation-
embryonic development- birth- maturity- ageing.

Stages of ontogeny

 Fertilisation- fusion of sperm and oocyte (zygote), restores diploid chromosome
number, activates early gene expression.

 Cleavage- rapid mitotic divisions without growth. Forms morula- blastocyst.

 Gastrulation-formation of three germ layers; ectoderm- skin, nervous system.
Mesoderm- muscle, bone, blood. Endoderm- gut, liver, lungs.

 Organogenesis- germ layers differentiate into organs and systems, pattern
formation and morphogenesis occur.

 Foetal development- growth, maturation, refinement of organ systems.

 Postnatal development- growth, neural development, immune maturation

 Maturity- reproductive capability reached, homeostasis stabilised.

 Senescence (Ageing)- gradual decline in physiological function, uncreased
susceptibility to disease.



Osteogenesis

 Is the process by which bone tissue forms (beginning in embryo and continues
through childhood and adulthood).

Function of osteogenesis

 Formation of skeletal framework

 Protection of organs

 Enabling movement

 Mineral storage

 Blood cell production

Types of ossification

 Intramembranous ossification- forms flat bones (Skull bones, mandible, clavicle
(partially))

Process

 Mesenchymal cells cluster- differentiate into osteoblasts

 Osteoblasts secrete osteoid (unmineralized bone matrix)

 Osteoid becomes mineralised with calcium salts

 Osteoblasts trapped in matrix become osteocytes

,  Trabeculae form- compact bone develops at edge

Key features

 No cartilage template

 Direct bone formation

 Produces spongy bone first, then compact bone.

Endochrondral ossification

 Forms long bones and most of the skeleton

Process

 Hyaline cartilage model- forms in embryo

 Cartilage grows- chondrocytes enlarge and die

 Primary ossification centre forms in diaphysis

 Blood vessels invade- bring osteoblasts

 Secondary ossification centres forms in epiphyses

 Growth plates (epiphyseal plate) remains for lengthening

 Plate ossifies at puberty- growth stops

Bone growth

Longitudinal growth (occurs at epiphyseal plate)

 Zone of resting cartilage

 Zone of proliferation

 Zone of hypertrophy

 Zone of calcification

 Zone of ossification

 Growth stops when the plate becomes the epiphyseal line.

Appositional growth (width)

 Osteoblasts add bone to outer surface

 Osteoclast remove bone from inner surface- maintains proper thickness and
medullary cavity size.




Osteogenesis: intramembranous ossification

 Process in which bone develops directly from mesenchymal tissue, without a
cartilage template, it forms flat bones of the skull, the mandible and part of the
clavicle.

 Where it occurs- flat bones of the cranial vault, mandible, clavicle, facial bones

Overview of the process

 Mesenchymal cell condensation (mesenchymal stem cells cluster in connective
tissue membranes. They differentiate into osteoprogenitor cells then osteoblasts.
This forms an ossification center).